This, the military version of the the 31659 chronograph, was included as a non-functional addition in a lot auction with another fully functional early-nineties collectors' Sturmanskie. Although the mechanics of the watch were faulty, the visible components are all in very good condition, which is becoming increasingly rare to find, and I was able to fully restore the movement to it's former glory.
The movement as it looked upon prying open the case back. Notice the "4-90" (April, 1990) stamped on the balance bridge. She's a beauty!
At the end of the lever, there is a spring that, when the function is activated by pulling out the crown, makes contact with the balance wheel and stops the watch. In order to view the tiny spring at the end of the lever, you will have to click on the image to view the high-res version of this image.
Pictured with the other Sturmanskie in the lot that was the main feature of the eBay auction (Nov. '13).
Leather NATO strap on a Soviet BBC Sturmanskie. The pinball game is actually much older than the watch!