The Mosin Nagant rifles from the importers are all "refurbs" imported from one or more of the former Soviet republics.
Being the paranoid suspicious commies that they were, the USSR never threw away any weapons, obsolete or not. After WWII, they gathered up all the Mosins and warehoused them. Over the years, up into the late sixties, they refurbished them, dipped them in cosmoline, packed them in crates, and stored them in strategic stockpiles throughout the USSR. That's where all the hundred dollar Mosins are coming from.
These rifles were assembled from piles of refurbished parts, stripped from all the original rifles. The original serial numbers on numbered parts were "force matched", ground or sanded off, or marked through, and new matching numbers were stamped or electro-penciled on.
They are in "issuable" condition. Aside from needing to be thoroughly cleaned, they should be ready to shoot. Don't expect any shiny bores though. For an extra measure of safety, you might want to have a gunsmith look it over and check the headspace.