Your dad might have been pulling your leg regarding the notch (Snopes) or maybe it was used for that purpose but that wasn't the intention. Another site says the notch wasn't so much for alignment in the stamping machine as it was for "The Model 70 "Addressograph". I was, however, confused by the last sentence in that second link: "Today, the notched tag is no longer used by the US government and has been replaced by one tag placed on a short chain, 5.5" long, commonly referred to as the "Toe Tag"." I think I read somewhere that the second tag on the short chain hung from the longer neck chain with tag so the two tags didn't clank against each other. Dunno'