[Nick]

Is the bolt from M.90 or from M.95? Is the magazine from M.90 or from M.95?

 

[Nick]

Here are some pictures:

PS. John, please, enable your PM; I have a question regarding a CA (Arsenal Sofia) marked clip.

 

[Nick]

That's exactly how this barrel looks, either not fired much or not at all (until now anyway) - VERY strong clear rifling...

Your barrel is a post-WWI replacement. The stamp Stf (Staatsfabrik) and the new style eagle are all post-war.