That's a partisan buckle, 1st class. You can tell from the gold star, and the fact it is attached with Russian chewing gum. Lesser partisans were forced to wear green stars attached by rivets. Equality indeed. :D
A field-converted German WWII belt buckle, now "sovietized." I was told this was worn by partisans, but don't necessarily believe the story. It was purchased inexpensively enough and cheaper than non-such-modified German WWII belt buckles that I believe this to be originally done field modification.
Can be partisan, but can be a regular Red Army soldier as well. I have seen plenty of photographs of Soviet and Polish soldiers wearing modified german belts, altough the belts themselves are harder to obtain.