Poljot Chronograph, Cal. 3133
(Made in Russia)

An unsuccessful opening attempt (the pic shows the partially removed opening marks)

The case back is a very soft steel and the case is brass. And the case back sits too tight. That is why I had to quit attempting to open the watch. But also thanks to the very soft materials, the opening marks could be filed and polished relatively easily. Until the watch needs a service, it will remain closed.