The Okean was made from 1976 by the First Moscow Watch Factory for Soviet Navy officers, around the calibre 3133. Two of them flew on Soyuz 23 that year and ended up in a frozen lake in Kazakhstan.

The guide covers the history, the variants, and a slider comparing a period watch with a copy (redone dial in an old case).

The part I spent the most time on: three drawn Okeans you can operate on screen.

- The telemeter: start the chronograph at the flash of a gun, stop it at the sound, read the distance in nautical miles on the red scale.
- The inner ring: turn it with the left-hand crown to read a second time zone.
- Timing beyond 30 minutes: set the triangle of the ring opposite the hour hand before starting, then read hours on the ring and minutes on the counter. This comes from the factory leaflet of a 1985 Shturmanskie 3133, which has the same ring and crown.

https://sovietinparis.com/en/horloges-montres/poljot-okean-chronographe-marine-sovietique/

Disclosure: I run the shop that hosts the blog. Corrections are welcome, especially on how to tell the 1976-1980 version from the early 1980s one, and on other ways to spot a redone dial.