Thomas Preik, a Master Watchmaker, started his career at companies Helmut Sinn and A. Lange & Sohne Glashutte/Sa, before moving into the manufacture of sapphire casebacks through his company Custom Watch Concepts (that is, in addition to offering his own Preik watches).
While we have never owned his sapphire casebacks, they have a very strong reputation in the watch community (and we will be purchasing one just as soon as we find a Omega 105.003…). Thomas offers a selection of casebacks for specific models of Rolex (quite a few), Omega (a good number), and a few Zenith and Breitling. His casebacks are made of sapphire crystal, are waterproof and acid resistant (1000ft / 300m / 30 ATM tested), are the same height as the original steel back (though some reviews say otherwise), and the Rolex casebacks fit on original Rolex case opener tools. If switching to one of these casebacks, we recommend taking to a watchmaker who can install the caseback and pressure test the watch.
The casebacks look very well finished, and are quite reasonably priced – absolutely worthwhile if you would like to easily enjoy viewing the movement. Yes, this replacing the caseback will void a manufacturer warranty (if one still exists…wouldn’t apply to our vintage pieces) and watchmaker service warranties, and yes, you should absolutely keep your original caseback to switch back if there are any issues or if you later sell the watch.
Some will argue that not all movements (particularly undecorated) are worth looking at, but to us it is more interesting than a steel casebacks (regardless of engraving…yes others will disagree with us here for certain). Some might prefer the feel of steel to sapphire on the wrist, or simply find it incongruous for a tool watch to have an clear caseback. But, well, we just like to look at movements. A lot. And if you are a vintage lover that wants to see the movement, at least you have an option with Custom Watch Concepts.
Note: if you research custom casebacks you’ll also find Swiss Watch Customs, another company that manufactured clear casebacks for Rolex. This company appears to have gone out of business in 2011.