If we are talking about same PM stamp, I have to disagree. It could not be ONLY post war stamp. My SA stamped, finn captured Izhevsk 1924 m91 dragoon also has the PM stamp like in the link in the row 6:I feel it's a post war mark. The 91/30 I saw had a PM 86 under the date. It also had a B inside of a circle (Budapest arsenal) on the stock. Sometimes the 91/30's will only be PM stamped, no number after it. If there's a list of Soviet organizations, one of them may match for PM, but it would only be a wild guess.