I've never heard the term "passed salvage gage" either; but I'll throw a theory on the table for discussion. If this gun was shipped mid to late 1949 (didn't see where the ship date for this gun was provided0; given the fact that the floor above the canal collasped in early 1949, could some materials have then become suspect? Although Smith machinery and equipment falling into the canal was salvaged, it was never put back into operation; so from that point forward the balance of Smith gun production was generated from parts already on hand. Is it possible that some barrel stock was somehow impacted and reclassified as "salvaged material" after the floor collaspe; maybe for insurance settlement requirements and therefore required to undergo additional proofing and/or inspection prior to being used? An interesting piece of trivia, do the folks at Cody have information in this regard?