I have 2 Camillus Mk1s; the first is stamped U.S.N. and has a steel pommel nut, the second is stamped U.S.N. over MARK 1 and has a brass pommel nut. Can anyone tell me which, if either, is the earliest stamping...or if they might have both been used concurrently? I have my suspicions the former may be earliest, but have found nothing to support it.