John,
I'm no expert,but I think it's a lost cause.It is likely that whoever refinished the stock spent a considerable amount of time "steaming" the stamps to raise the dings back up.Also, when it was sanded,the sandpaper was likely backed up with a block, especially to level the surface.Furthermore, the stock finish will fill low areas,especially if sanded with a block. There is a small possibility that some of the numbers would showup, if you remove the finish( with acetone or MEK, it has been sanded enough already)and look at it at an angle under a strong light. You would have to be the one to decide to damage the finish, for a small chance of success. It would have had the "D" stamp and maybe the "K M" stamp. Good luck.
Mike