When referring to case numbers, note that the number is only engraved on the caseback. Numbers are not engraved on the case, such as between the lugs, or on the movement.
There are three different production batches (generally know as “Marks”) that are referenced when discussing Zenith A386s, based upon grouping of case numbers (see Zenith A386 Casebacks and Interiors section). Each A386, if correct, has a specific combination of case, sub-register hands, caseback and crown. You may see cases paired with incorrect casebacks, so if you try to identify solely based on case(back) number, that may lead to believe it is a believe the watch is from a different production.
The Mk 1 case is generally recognized as being the most rare, with estimates at <500 pieces in total, though not confirmed by Zenith. The final production batch, known as Mk 3, may be sub-divided into three other groups, for a total of five production batches. References are generally made to Mk 1-3, instead of Mk 1-5, as the watches produced in the final three production batches were all the same in combination of design of case and caseback. All cases are 38mm with 19mm lugs. The Mark 1 and Mark 2 are 9mm, plus 2mm for the plexi (11mm in total), and the Mark 3 is 10mm (1mm thicker due to different caseback with star), plus 2mm for plexi (12mm in total). The Mark 1 stands out versus the later product batches in that there is no groove in the case where the lugs merge into the body, it is a seamless transition to the flat top (see image below). Both the Mark 2 and Mark 3 feature this groove. The difference between the Mk 2 and Mk 3 batches are the caseback, with the Mk 3 featuring the “NATO” star, such as with the others from this period, the A384 and A385, and the A3817 and A3818. Other Zenith wathces with the flat caseback include the A787 and A788. ‘sempervivens’ posted a nice overview of the stainless steel Zenith El Primeros from 1969-1975.
There are bezels only at the top outside edges of the lugs. Bevels on the top inside of the lugs are due to polishing, and are not original to the watch.
The watch has tritium in the handset, chronograph seconds hand, and index hour marks.
There is a Zenith A386-like watch that you may see that make you look twice. [Alert, alert! Correction ahead! Thanks OmegaForum crew!] Claimed as movement 3019 PHC, reference number WH 40801 from 1969, this can be seen in Roseller’s book, and made in 10 pieces. While I had first assumed it to be made-up like his “Unicorn”, images of similar watches appear in Zenith catalogs. Roseller’s book does not have an image, rather a reference number (other images can be found for the watch in gold, as well as in white gold with diamond bezel).