~1992 ran into a fellow that bought a Mosin-Nagant that had a strange purple waxy stuff slightly oozing from under the buttplate. He took off the buttplate and just as you suggest, found a roll of obviously elderly onion skin paper with minute Russian writing on it. He didn't know Russian and it took him a while but finally found a professor at, I think U of I (which ironically is in Moscow, Idaho!) who was Estonian or Latvian I think, regardless, who read and understood Russian. The woman translated the writing for him. Turns out it was from a Russian soldier who defected at the end of World War 2, taking advantage of the momentary chaos to cross the Bering Strait w/ some others and hide out in Alaska. As memory serves, he worked his way down thru Alaska, eventually being connected to a contact in Vancouver, Canada who was part of a "underground railroad" assisting defectors. I think a doctor or dentist. The Russian afterwards slipped into the USA and settled in Montana, doing woods work. He cited being married and having a baby and then the story ended.

Our guy found the rifle at a swap meet and had it for some time before deciding to investigate the purple stuff, which turned out to be candle wax.