Yeah, your bike is an IZH 49 for sure. They only made that one model with plunger rear suspesion. The earlier IZH 350 had a rigid rear wheel and the later Jupiter and Planeta had swingarm suspension.
The make, of course, came to be only after the Russians took the production facilities of the German DKW works with them after WWII and
re-erected them in Izhevsk in southern Russia.
The IZH 350 was almost an exact copy of the DKW NZ 350.
Here are some more pics of how your bike should look like.
Cheers