At the end of WWII, Germany was flattened and people were doing anything for a few dollars or enough to eat. One thing they did, if they had the skill, was to engrave guns for American GI's. Like all engraving, some was beautiful, some not so. The term used was "carton of cigarettes engraving" because that was what it generally cost. (Cigarettes were $.25 a pack or so, but the military issued them at no cost. Quite a change from the official position on smoking today.)
After looking more closely, that engraving is quite a bit better than that seen on some other guns, so it is possible it was done through a PX, which was common later on. The reason I say that is that a K-200 would not have been available to an American right after the war, but would have been sold in the PX in the 1950's or 1960's.
Jim