It could be a Finnishrework, but it has a pot belly so I'm thinking Finn one peice.
The Finns salvaged everything. I have a Finned 91 with a double sling slot
M27 ski rifle butt grafted (two piece Finn style) to a 91 forend.
You never know what your going to find on a Finnish Mosin Nagant.
Here's a good sight on Mosin Nagants including Finnish rifles.
7.62x54r.net
You can also find out how rare your rifle is on that sight too.