Care & Servicing

How to report your stolen watch

First, condolences. I hate thieves, and I hate that watches get stolen. And I hope that the
Alpha hands stolen watch registry or another stolen watch database can help recover your timepiece.

What to do when your watch is stolen:
1. First things first: file a police report. If you haven’t done that, it is a necessary first step. Without a police report and the ability to prove ownership, the possibility of recovery is infinitesimally small. You’ll need to provide details, such as the unique serial number (or other unique characteristics), for the report.

2. Submit your watch to the Alpha Hands stolen watch registry, one of the other known stolen watch registries, to the appropriate manufacturer if they maintain a stolen watch database (such as Rolex), and share liberally online in forums. The more people that know the watch is stolen, the better. Some people don’t like to share stolen watch serial numbers online, which I confess I don’t understand.

3. If you locate the stolen watch, my opinion is to not try to directly engage with seller/reseller for fear they could be scared off and the chance to recover the watch disappears. I would personally engage a third party in recovering the watch before the police get involved. Individuals such as Chris Marinello at Art Recovery International, have expertise in this area and are incented to recover the watch.

Wearing and use

Please, don’t stick that vintage watch away in a safe, put it on your wrist – enjoy it and show it off on IG for the rest of us to check out!

Some caveats:
– If your dive watch was originally intended to be waterproof and noted so, you can still use it as such – just swap out that nice leather strap, make sure to have your watch regularly serviced (perhaps more frequently than if you aren’t wearing in the water), and have it pressure tested (this is a “dry” test) by your watchmaker. Depending on how much you use the watch in the water, you may want to consider getting it pressure tested by your watchmaker regularly. We’ll comment that many collectors won’t take their vintage dive watches anywhere near water, and prefer swapping to a modern watch when hitting the water. We can’t say whether or not they have read this excellent and entertaining post on vintage watches and water Myth Busting…. again. If you do take it for a dive, rinse afterwards – salt may impact older watch material, and you don’t want any corrosion (similar for chlorine).

– Dust and humidity, including rain, are not friends of your vintage watch. If you are going to hang out at the pool or do some gardening, consider swapping off that vintage chronograph (more pushers = more entry points) for a modern watch. If your waterproof watches is fogging, moisture must have entered the watch (or moisture was in the watch when sealed), so you may want to have it checked by your watchmaker.

If you do live a humid environment, or are headed on vacation, it is important to understand what types of cases will protect your watch from moisture. The Rolex Oyster case (1926), Gallet Clamshell 4-screw case (1936, built upon rights to a “waterproof” design (Brevet N° 189190) from Schmitz Frères & Cie) and super compressor cases (1950s+ from E. Piquerez S.A., both here and here) cases, all of which offered a degree of protection. But don’t expect upon purchase that your vintage piece, regardless of source, is waterproof – it’s a good idea to make sure the watch and seals are in good condition and that it passes a pressure test.

Some collectors are comfortable traveling to humid locations, or simply in and out of areas with vastly different temperatures (think of existing a nice air conditioned building out into the Florida heat), and believe that leaving the crown open will allow the watch to “breathe” and pass the air in…and back out of the watch. I wouldn’t personally do that, preferring to make sure it’s been testing, and the crown is secured.

Winding and watch winders

Winding and setting the time
To wind a manual watch, simply rotate the crown clockwise until you feel some resistance, then stop (for a stopped watch, this will generally be in a range of 25-30 turns of the crown). Automatic watches (which wind themselves as you wear them) may require just a bit of winding to get started. They won’t provide the feedback when fully wound, however.

From our completely unscientific survey, we found that both watchmakers, as well as the rest of us, are split as to whether they turn the crown of the watch in one direction only to wind, briefly releasing between each motion, versus holding on to the crown the entire time while winding, moving back and forth in both directions. We haven’t found an example of a watch with wear due to the rocking back and forth while winding, but in theory there can me some minimal amount, so if you reeeeally care about the fringes and you “merely look after [the watch] for the next generation” ™, then maybe just one direction is for you.

For setting the time, always advance time forward, with the exception of small movements when setting the precise time. Be aware that there are watches with complications that you do not want to adjust during certain periods during the day (really during the evening period around midnight related to date changes). For those we generally stay away from making adjustments during a wide range of time, say 9PM – 3AM.

A bonus note: not all watches set by winding the crown in the same direction! Most of mine, for example, set by turning the crown clockwise, but others to set counter-clockwise (I didn’t learn this until I had made a handful of purchases).

Some chronograph owners leave the movement running all the time. This likely results in negligible additional wear on components, but will reduce the power reserve (how long the watch can run without being wound) and result in more frequent servicing required.

Watch winders
Watch winders are not a necessity, they are more for practicality – either so you don’t have to wind them, or that you have an automatic perpetual calendar watch where it is a PITA to set the date (if no quick set). If you do want a winder, consider a model that can be adjusted, and keeps the same amount of wind in the spring as when you put the watch in the winder.

We haven’t seen examples of additional wear on a watch from a winder versus manually winding. Our personal opinion, based on nothing, is that it is just as good, or better, to leave the watch unwound until we want to use it. There should not be any issue with letting the oils sit…and if there in an issue, by that time our watch is probably due for a service. And yes, we enjoy winding our watches ☺ For those watches that we rarely wear, we pull them out and wind them every few months.

Where to find vintage watch parts

We will look on:
– eBay
– forums

And in terms of dealers/stores that sell, you may wish to try: We used them for an old NOS Heuer Carrera crystal, and they carry a wide variety of items (movement parts, crystal, crowns, etc.). Parts come and go, so you’ll want to visit them regularly to see if what you are looking for crops up.

Radium in vintage watches and health concerns

Those vintage hour numbers, indices, plots and hands that glow on their own (termed radioluminescent, as opposed to photoluminescent, which requires light to charge)? That might just be radium, and furthermore, it could be enough you should do a bit of research. People accept different levels of risk related to radioactive material, so I can’t tell you whether it is “safe” to wear your watch, or if the radium in your watch can do harm (at the least, make sure the watch stays in one piece and remains closed…though even then, gamma particles can still make their way through crystal and metal).

What is lume/radium
When people refer to lume with radium, they are talking about radium salts mixed with a chemical phosphor, which results in a compound then developed into a luminescent paint. The paint (lume) glows due to mixing, though over time the glow of the paint will fade as the fluorescence of the mixture degrades due to the radium. The radium is still there (and will be for a long, long time… it has a 1,600 (!) year half-life), in amounts nearly as high as when the watch was made, though the compound no longer emits as much light. So don’t think just because your vintage watch doesn’t emit light, it no longer poses a hazard. By the late 1960s, radium was phased out and replaced with much safer alternatives.

How to know if your vintage watch has radioactive material
The easiest and most reliable way to know the level of radioactivity of your watch is to purchase a Geiger counter. Reasonably accurate devices are not inexpensive, starting at the level of the RAXED 1053, for example. Others to check out include the Mazur Instruments PRM-9000 and SOEKS 01M. Another route some collectors and watchmakers to save some dollars is to purchase old military surplus Geiger counters (just make sure you calibrate!).

Outside of going to the trouble of purchasing a Geiger counter, text on your watch dial may provide some information on the level of radioactivity at time of production:

  • Swiss: made in Switzerland. If it has luminous markers, and made prior to the 1960s, then the watch most likely has radium. After 1998, watches may have Swiss or Swiss Made on the dial, however by this time LumiNova was used instead of radium.
  • T: indicates that tritium was used, as opposed to radium. Tritium, introduced in the early 1960s, had replaced radium (Radium-226) in watches largely by the end of the 1960s, and although still radioactive and potentially hazardous, the beta particles are not able to escape through the watch glass or skin (but it is a health threat if ingested). Both tritium (H-3, half-life of 12.3 years) and promethium (Pm-147, 2.6 year half-life) are radionuclides, but emit much lower levels of radiation than radium (Ra-226). With promethium’s relatively short useful life span, it was replaced by tritium.

    With the introduction of tritium came new markings on the dial, with “T” added to watch dials circa 1963. Tritium was used until 1998.

  • R: at the same time “T” was added, dials “R” or “Ra” were added, indicating radium [9]
  • Swiss T: a watch that is Swiss made, and with less than 5.0 mCi (mCi is a millicurie, a unit of measuring radioactivity).
  • T Swiss T: Swiss made, contains tritium and emits less than 7.5 mCi [10]
  • Swiss T<25: Swiss made, contains tritium and emits less than 25.0 mCi [10]
  • Pm: contains promethium (may be designated by P, Pm, or Pm 0.5) [10]
  • L Swiss L: optional marking indicating that the lume is photoluminescent (due to exciting the luminous radiation, as opposed to radioluminescent, which is due to the radioactivity of the material) [10]
  • Rolex (and Tudor) timepieces will have additional symbols to indicate different levels of radium. The “exclamation point”, where a small dot is below the index marker at 6 o’clock (first seen in 1962), indicates that the piece is following Atomic Energy Commission regulations from 1960 and has lower radiation levels. The underline on the dial (seen starting in 1963) was used to indicate still lower radiation levels, in line with <25 millicuries of tritium. [11]
  • Optional markings: The ISO standard governing dial marking (ISO 3157: Radioluminescence for time measurement instruments — Specifications), which limits material to tritium and promethium, doesn’t require any marks/marketing if there is less than a certain level of radiation in the watch [10]. These dials may optionally be marked with T or Pm.
  • Symbols: military watches have markings that designate levels of radiation, such as Circle T, Red Circle 3H, H3 and radiation symbol (required starting in 1975 to indicate tritium) [12], Yellow Circle with Red Triangle Nuclear mark, and Triangle Nuclear mark.
  • σ T SWISS T σ : does not indicate radioactivity, but rather was used for a period of time to signify that the markers and/or dials are made of gold (white or yellow), and a designation selected by members of APRIOR, the “Association pour la Promotion Industrielle de l’ Or”, an industry association for those making gold watches. This designation was mostly used around 1970.


How often and where should I service my vintage watch?

How often to service your watch
All watches require service, and the length of time between services will depend on how often you use and wear the watch, and the complexity of the watch. Depending on the source, recommendations range from every 3-4 years, up to 10 or more years. Most collectors seem to gravitate to a range of every 7-10 years. And yes, there are people on forums who will post about how their watch hasn’t been serviced in 35 years and keeps great time. More power to them!

If you swim and/or dive with your watch, having it pressure-tested on a far more regular basis, even yearly, is recommended. You don’t want to find out when you watch needs to be serviced based on seeing water inside.

Where to service your watch
We have found watchmakers through a combination of friends, acquaintances, watch forums, and the AWCI. After working with a few, we then start to gravitate to those we would use regularly. But first, it will be a big help to but your expectations in check – it isn’t likely that you can drop your watch off today and pick it up next week. We have had standard services that took anywhere from a month from initial contact to the watchmaker to having it back in our hands, to nearly two years. This will range depending on how busy the watchmaker is (can be months before you even reach the front of the queue), how complex the watch is, and what type of servicing or replacement parts are required.

Whomever you use, make that you and your watchmaker are on the same page with what type or work will be done and what parts will/may be replaced. Then get that in writing. Signed in blood would be ideal, but generally not practical. Otherwise you will wind up with horror stories of what happens to your watch like this one or this one.

Your watches can be made to look brand new, but keep in mind most collectors will want them in as original condition as possible. So if you want to try to keep the value in case of resale, you should think twice before polishing away dings and scratches, replacing the dial (embrace the patina/”tropical”/crazing) or hands, reluming, changing the crystal, swapping a faded or cracked bezel, and tossing away an original bracelet. If you do decide to replace anything, at least hang on to the original parts.

Insure your watch when shipped as necessary (some personal article insurance policies will cover insurance during shipping). Make sure to pack it well – we recommend using a plastic membrane shipping box with surrounding material for additional cushion and protection. We will double-box watches (hey, FedEx-labeled boxes are free!), because we are just that worried about keeping them safe – it makes it more difficult for someone to quickly tear open two boxes to pull something out, and moving to a larger size box (say packing the watch in a small box within a medium box) somewhat obfuscates what is inside. Oh, and if there is an alternate ‘Ship To’ name other than “Ted’s Vintage Rolex Watch Repair Company”, not a bad to use that.

Last, before dropping off or sending for servicing, be sure to take pictures of the watch in as much detail as possible for your records in case any issues arise, such as theft, damage to the watch, or if the watch is lost in transit. And if you don’t have recent pictures of the movement, you may wish to ask for those also.

Options/resources for servicing:
Watch manufacturers
Sending your watch for service from the original manufacturer is one option that may be available, but not necessarily the one that ensures the best service. Just as with other watchmakers, there are horror stories of vintage watches going for service at the manufacturer and coming back with relumed hands, replaced dials, and polished, obliterating the value of the watch to a collector. In addition, you will often find that the original manufacturer will take much longer, and will charge much more, than an independent watchmaker.

However, on occasion you may find that the only source for parts is the original manufacturer. We’ve found this to be the case for a Gallet MultiChron with Excelsior Park 40 movement, which requires a trip to Gallet Watch Service in order to be able to get the original T-end mainspring, which is not otherwise available.

Independent watchmakers
Your watch is so old there isn’t a warranty anymore, so go ahead and service it where you please. If you are having trouble finding a good watchmaker in your area, keep in mind you don’t need to work locally. With relatively few competent watchmakers, you may find someone you wish to use in a different corner of the world. Not a problem – just familiarize yourself with them, confirm that they carry insurance and their safety precautions.

American Watchmakers-Clockmakers Institute (AHCI)
The American Watchmakers-Clockmakers Institute (AHCI) provides a listing of watchmakers that are CW21/CMW21 certified (Certified Watchmaker and Certified Master Watchmaker for the 21st Century), as well as individuals without formal training. But keep in mind that anyone can be listed in the AHCI directory simply by paying the yearly fee – there are no tests, backgrounds, or qualifications required (yes you could join today)! Are there non-certified watchmakers that will do good work? Absolutely. Have we used them? Yes. But do your background research before entrusting your watch to someone for the first time, including making sure the watchmaker carries appropriate insurance and takes safety precautions.

Insuring your watch

Regardless the value of your collection, if you are concerned with financial loss, we always recommend a good insurance policy. Even with all the tales of pieces gone missing, nearly 40% of survey respondents don’t carry watch insurance.

I am frankly surprised that so many collectors don’t insure their watches, or at least consider it. Perhaps people don’t have a sense for the costs and fear it will be exorbitant, or believe that it is just an pain in the backside in order to get a policy or update it. Urban myths, people. Specific to ease…it can be simple to add and remove watches from polices – no receipts/appraisals, no notary, no photos…just provide manufacturer, serial and value. What HODINKEE Insurance isn’t anything new – this simplicity has been available for ages. What they are doing, however, is giving watch insurance its due. And that, in my opinion, is a big plus.

Some ask what insurance carrier to consider, and there are a few that come up repeatedly specific to watch polices (and where item coverage is available):
– Chubb (underwriters for HODINKEE Insurance), such as the Chubb Masterpiece Valuable Articles policy
– Nationwide / Nationwide Private Client
Jewelers Mutual

There are a couple of basic ways to insure your watches:
1. Personal articles/personal items/collection policy (this will specifically list pieces and value)
2. Blanket coverage
3. Renters/homeowners (blanket insurance for watches may or may not be included in this)

Policies range from the most basic, to full-blown covering while traveling, during servicing, and even when shipping (a nice feature so you don’t have to purchase additional insurance coverage from your shipper…you do service your watches, right?). You might be tempted to look at the cost of the policy as a % of the value of your watches, which is fine…but you may be comparing apples to oranges when looking across different insurance agencies, which have wildly different terms.

For each watch that is covered, you should have ALL SERIAL NUMBERS, photos, any details/description including unique characteristics such as personal engraving, original purchase information, and current estimate of value. And please…we hear stories of individuals who have pieces stolen at the time they have tried to sell them (either by robbery or in shipping), and they had cancelled their insurance on the piece before the transaction was finalized. Don’t do this!

It is beyond surprising to me how many watches are stolen and the owner does not know the a serial number – I see mid-single digit percentages of those who reported stolen watches to the police providing a serial number. Crazy.

Depending on your insurance provider, you may get a discount for keeping your watches in a safe deposit box or a home safe. In this case, there generally are minimum home safe requirements, such as the weight and/or how attached to your residence, and UL rating.

Keeping your collection safe

There are a few different options on where to keep your collection.

Watch storage options
1. Safe deposit box
If you choose to keep your watches at the bank, you won’t (really) have to worry about theft or natural disasters (of course, you may have to worry about Wells Fargo losing your goods, and you are left with no recourse). And of course, it is a PITA if you want to regularly swap watches, and you don’t get to enjoy your collection in the comfort of your own home on a moment’s notice.

In my non-scientific Instagram poll of where owners keep their watches, 50% selected safe deposit boxes.

Options if you are considering keeping them at home:

2. A safe
If you prefer easier access to your pieces, consider a home safe. These range wildly in term of construction (but I mean, who doesn’t need a BUBEN&ZORWEG X-007 EXTREME or a Man Safe?).

If you are going to make the investment, consider something substantial that can’t easily be penetrated or carried out your front door. See the section on home safe burglary and fire ratings for detailed information and a listing of safe manufacturers to consider. If you are worried about where you will fit a safe, know that there are a variety of sizes and weights from the most well-known manufacturers, such as American Security (AMSEC), as well as some manufacturers such as Prestige Safes that can make a number of models in custom sizes at no extra charge.

A nice benefit of having a (decent sized) home safe is the other items that you will find a place for inside – passports and other identification, legal documents, titles, backup hard drives, etc.

And if not a safe, at least make sure you have a decent lock on the door of your watch room.

3. Right out in the open, in a beautiful display box, perhaps.
With this selection, you can enjoy all the watches whenever you like. And your friends can do. And even your spouse, who may be long since tired about your obsession, but is kindly putting up with this hobby.

You may be able to pair this option with a safe if you have a display box (or multiple boxes) that are sized to be able to slip into the safe when you are away for longer periods of time, or when your kids are throwing a house party. Keep in mind that some manufacturers can make safes of custom sizes (and even at no extra cost).

4. Back of your sock drawer
No. Just, no. Burglars will look there, and you don’t even get to enjoy looking at your collection. Of course, the upside is that they are easily accessible. So accessible that if you forget and yank socks out of the drawer quickly, you even may have the opportunity to enjoy them as they sail past you on the way to the floor.

While 30% of respondents to my poll keep watches “hidden” in their sock drawer or the like, I don’t recommend it.

Regardless of which option you select above, depending on the value of the pieces in your collection you may want to consider insurance to cover them. Read more in our section on ‘Insuring your watch’.

Home safe burglary and fire ratings

If you decide a home safe is the route to take to store your collection, it is useful to brush up on the different levels of burglary and fire protection that are available.

Good-to-know: some manufacturers can make custom-sized safes at the same cost at the “standard” sizes. With this benefit, you can select the right size to fit an appropriate location in your home, and even design to fit whatever you will be placing in the safe (watch display boxes, hard drives, computers, paperwork, etc.).

Some manufacturers to consider:
American Security
Brown Safe
Prestige Safe (many of their safes are made to order, so you can select any size or shape, at no additional cost)

As for the specs of the safe and your home, being risk-averse I recommend:
1. TL-15 Rated safe weighing enough that no thief is going to be able to carry out without some serious assistance (if they were even able to unbolt it from your dwelling)
2. Group 2M mechanical lock
3. Class 350 degree 2 hour fire rating: interior temperature not above 350 degrees when subjected to 2 hours at 1850 degrees
4. Home alarm

Burglary Ratings and Classifications
Please don’t purchase safes with the following ratings:
No recognized rating
The only rating on these is from the manufacturer itself (no UL rating). Avoid.

Theft resistant
The safe has a lock. That’s it. Your office file cabinet has the same rating.

RSC (Residential Security Container) TL-5 rating
UL-rated, yes, but can only withstand an assault by a thief with basic household tools (crow bar, screwdriver, hammer, drill, etc.) for up to 5 minutes. Beware of safes that blend steel plating with drywall fireproofing panels. Tip-offs for these will be weight – the heavier the better. Most home burglaries are over in 12 minutes. This safe will probably only help you out if you are in the home and the thief is someone you have let in and is either a guest or perhaps working within the home, so you’ll be able to hear any attempt to open.

Safe classifications worthwhile to consider
The following are Construction Ratings, established by the insurance industry
Class B rating (“B” Rate Construction)
This rating is not standardized across the industry, and while in theory a step up from RSC TL-5, these have not been UL tested. These safes most often have a 3/16″ to 1/4″ thick steel body with a 1/2″ thick steel door. Note that the thickness measurement provided is the total thickness on a side, including any material sandwiched in between other plates (so a Class B safe may have two pieces of 1/8″ steel with material in between). I recommend a UL rated safe.

Class C Rating (“C” Rate Construction)
Double the weight of Class B, and double the steel thickness all around.
As with “B” Rate Construction, this rating is not standardized across the industry, and while a step up from Class B, these also have not been UL tested. Again, this is not my recommendation.

If you are really serious…these will help to keep thieves at bay for a while
UL (Underwriters Laboratories) rated safes
TL-15 Rating
A burglary rating provided by UL, TL-15 guarantees the safe is capable of withstanding sustained attack from a seasoned safecracker with an assistant and intimate knowledge of the safe’s inner workings. To pass this test, the safe must resist high-powered specific safecracking tools using by professional thieves for at least 15 minutes on the door (an additional 8 minutes on the body). The 15 minutes is the actual working time on the safe…when the tools are physically touching the safe and attempting to open. Tools for this rating include common hand tools, drills, punches, hammers, etc.

TL-30 Rating
As with TL-15, but resistant for at least 30 minutes (and an additional 8 minutes on the door), and some additional tools.
A TL-30×6 rating provides for testing on all 6 sides of the safe. A TRTL-30 rated safe can handle 30 minutes of attack with a torch and other advanced tools with high speed drills, saws with caribide bits, etc.

Lock Ratings
Some choose electronic locks for their ease-of-use, others go with the old standby mechanical locks (the dial you spin back and forth). Pacific Lock has a nice safe lock reference guide.

Electronic Locks
Group 1 (“UL Type 1”)
If you go with an electronic lock, you’ll want a UL Type 1. UL 2058 (the primary standard for electronic safe locks) has just one grade, so you will want to make sure if you select an electronic lock that it is UL Type 1. For these rating, batteries much be stored outside of the safe (in the keypad mechanism), the safe combination must be stored in non-volatile memory (remains even after power is cut), and the processing of entry combination takes place within the safe.

Mechanical Locks
Most locksmiths I have spoken with prefer the old school mechanical locks, noting they hold up better over time, and easier to bypass if necessary. The arguments given in favor of for electronic locks is they are easier to use if you need to get into your safe extremely quickly, if you need to regularly change the combination (and want to do so on your own), and are going to access on a very frequent basis (say, multiple times per hour).

A mechanical lock can be unlocked in roughly 10 second by someone who moved as a reasonable speed. Don’t believe nonsense such as this Dean Safe video that shows someone taking 30 seconds to open a mechanical lock.

Mechanical locks are rated based upon UL 768, which specify tolerance levels and defines attack resistance. All rated locks under UL 768 must provide at least 1 million possible combinations.

Group 2
The minimum rating. Using on B and C class safes (see above). Not recommended for higher rated containers, such as TL-15 and TL-30.

Group 2M
Most common, providing up to 2 man-hours of resistance, and used on TL-15 and TL-30 rates safes. I recommend use of a Group 2M or higher (Group 1 or 1R) lock.

Group 1
Incredibly safe, and recommended for TL-30×6 and TRTL-30 rated safes. Resists 20 man-hours of attack. Punching results in the lock being immobilized.

Group 1R
Beyond Group 1, and resist up to 20 hours of radiological (aka X-ray) attack.

Fire Ratings
UL offers the most comprehensive and stringent fire testing. The temperature on the UL label (i.e. Class 350) indicates the maximum interior safe temperature during testing. For reference, paper chars at 405 degrees F, with paper auto-igniting around 480 degrees F. Home fires can reach temperatures of 1100-1500 degrees F, with the highest temperatures at the ceiling and in the attic area – so hopefully far from where a safe would be positioned.

When purchasing a safe, you may also wish to ask how the safe reacts to high temperatures. Some safes have walls that expand with heat, providing additional protection, and some feature material such as Palusol and Flexilodice, which act as seals to expand at high temperatures and prevent access by flames, smoke or hot gases.

Both your environment and distance to fire station locations should play a role in your decision on appropriate fire rating, as these in turn determine how long a fire might be expected to burn uncontrolled at your home.

How to check if you watch keeps accurate time

Curious if your watch is keeping good time? Could it be better?
We don’t have a timegrapher (machine that takes measurements of the accuracy of watches), so we head to our local watchmaker to have them test for us.

If you have the results, or are curious what levels of accuracy you can (should?) expect, take a look at these links:
The Real Reasons Watch Reviews Don’t Talk (Much) About Accuracy
Why You Should Own A Timegrapher (and how to use it) (however, this is good as a basic explanation on timing numbers as well, even if you don’t have intentions of ever purchasing one)

Some good threads on Watchuseek
How do watchmakers measure accuracy
How to read the result from the machine that checks the accuracy of a watch

And if you are ready to get deep into the details, a good read from Witschi (manufacturer of timers):
Test and Measurement Technology for Mechanical Watches