[RyanE]

How is it that the imperial Russian markings did not get ground off under Soviet rule??

It's very possible these were never in the Soviet Union. Bulgaria disposed of a lot of their WWI captured M91 after 1918, but perhaps not all of them.

 

[RyanE]

I’m trying to remember the story here. The tony star between the date and the serial number is significant as to its origin. Someone will chime in for sure.

They are Bulgarian cutdowns of old M91s to M44 pattern carbines. The bayonet lugs were removed at some point, perhaps for export to the US (not uncommon even on bolt guns).