I have worked in a FED Gov. facility that overhauled, referbished and in general, repaired military weapons for the Army. It was our policy to refinish in the condition that it was accepted for repair. This could be true in the case of your UMC. From what you describe, appears to have been refinished, it may well have been done @ a Gov. agency facility.
As you mentioned, the lettering is well worn, as if from many polishings, could be attributed to the experience of the repairman at the Arsenal or Gov repair depot. I have seen them, at our shop, polised until the screw holes are oblong in just one process.
I have been to many Military Auctions, and I believe that the OLE man bought it for $100.00. I once bought 300 M14, match stocks for $3.00. Yeah, surprised me too. I thought I was buying 3 stocks, but actually was buying 3lots. (palets)