The Russian Mosin Nagant Forum

What do I stumble across? I know it's a 1945 Izhevsk in non refurb shape

That's a M-44? It's got a refurb stamp and arsenal repair stamp, I dunno SD

It is indeed a 44.

Looks like a couple of refurb markings on it.

The square with a line through it is a typical refurb mark. The "SD" above the serial number is an import addition - some imports have that translation of cyrillic letters into latin equivalents. The cyrillic "GR" is an unidentified Soviet marking seen on this page in photos 7B and 7C.
http://7.62x54r.net/MosinID/MosinMarks04.htm
I hope that helps you understand what you have a little better. Thanks for sharing!

That is one of the rifles that came in from Romania back in the 90's. These were Soviet refurbished rifles that went to Romania as military aid after WW2 ( or one of the other buffer states and then sent to Romania later), these were issued to the Romanian military and not refurbished again before being sent here. If it lacked the 90's Century Arms import mark it could have been a Korean war capture rifle, but not in this case. Nice find, not that many Soviet M44's came in with that lot, most were Polish, Hungarian, or Romanian made, plus a big pile of 91/30's.

A little background...

The square with a line through it is a typical refurb mark

This stamping represents a specific refurbishment/repair depot. Although we know where many of these depots were located, some, like this one, are unknown at the present time.

The "SD" above the serial number is an import addition

Early importers, I think in this case Century, could not duplicate most of the serial numbers with prefixes, so they translated the prefix and stamped it above the cyrillic prefix. This translated prefix/serial number combination was then stamped on the side of the receiver which became the official serial number of the rifle.

Looks like one of the M-44's that came out of Romania