looks like a 2204 slim. If the movement is stamped 1M43 (1st Moscow Watch Factory) it's an older one, too. Very nice watch, still does a brisk trade on the second hand market. Your dial is interesting because it doesn't have the tell-tale mistake of most of the modern fakes, but is missing the original surface.
I doubt this one has been tempered given its value and age, it is my granddad's watch so it has been here since sometime in the '70's
I did talked with my dad about granddads watches, and apparently he ran some watch import (mainly Russian watches) back in the days '70-'80. In the past employees here used to get engraved watches from the companies for their work anniversaries and retirement. My guess is that the markings got lost with cleaning/polishing, this one has few crystals changes, I had to polish it myself last month before changing the crystal after it was sitting in a drawer for years.