The serial number is certainly stamped in Cyrillic, suggesting that it is Russian; the s/n shown is "Sh Z 384", and it follows the Russian practice of two letters followed by three numbers. This is a submachine gun designed by Georgi Shpagin in 1940, and adopted by the Russians in 1941 as the "PPSh41"/"Pistolet-Pulemet Shpagina 1941". There may be a factory mark on the top cover showing when and where this one was built, but they saw widespread manufacture and use through the second half of WW2, and were copied by Russian satellites states and China after WW2. The Chinese and North Korean copies are usually marked in kanji ideographs, and woudn't be using Cyrillic lettering, so I would say it's definitely a Russian example. Has this one been fired, or is there a chance it might be fired? The Germans captured so many of these on the Eastern Front that large numbers of them were converted to 9mm, so make sure that it's in the proper chambering if it goes to the range. If you've got any specific questions, let me know, and I'll look through my Russian books.
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