We know from the log books of Yugos, that when in storage they were pulled periodically from the crates and inspected. I dont see why a similar instance may happen with russians and they simply record the inspection right on the stock. However, if these stamps originate when the stock was built.... common sense tells me they are QC stamps related to the manufacture of the stock itself which as RM suggest, wouldn't be of any use to a rework facility to reapply after refinishing a stock.