I found an old catalog (1953) online of Hamilton materials. It lists, under "crowns", 14/0 size, type 2, yellow gold, for the case model name "Myron", that the old part number is Refill 35, and that the new part number is 20101. My question is: why are Hamilton crowns that I see on the internet, in their small paper envelopes, designated with a a six digit number, as in 184206. Are these more current than 1953? I have not seen any that are five digit numbers.