I don't have many fossils from Russia but this is one of them that I bought off E-bay a couple of years ago. It's a Kosmoceras from Michailov, Russia that came out of an older collection. I like that some of the shell material is still preserved as a white rind on the otherwise pyrite replaced shell.
There is some damage to the fossil along the outer edge. but this does not detract from it too much.
One of the septa is exposed and coated with drusy pyrite.
I think this specimen was treated with a coating of some sort to preserve the fossil and prevent "pyrite rot" since there is little degradation. Kosmoceras is a genus of Ammonites that lived in the Callovian stage of the middle Jurassic.