h2u
Village Idiot
Wait, according to this, pinned rear sights became standard in Izhevsk M91/30's around 1940. That means that the pinned rear sight is original to this Mosin, not a retrofit feature.
http://7.62x54r.net/MosinID/MosinFeatures02.htm
Good catch! Forgot Izhevsk starting doing that standard
This could then easily be a non-refurb rifle. I believe I have a similar example from '42. Will have to dig up some pics and see if I caught the correct angles for any info.