There aren't a lot of surviving Enforcers. I like to see some info published on marking detail to validate the real mccoy's. The info I'Ve seen so far would indicate that Enforces 000 to 300 most likely had the single oval milled marking area. Sure exceptions exist and like to hear about these. After 300 believe the marking area was milled flat and then at some serial number marking was to the existing receiver profile...unissued receiver perhaps? Double lined milling appears to be for correction of marking.....perhaps Envoys made into Enforcers. Some oval dimensions would be great info to see.