Colt will not letter the 3rd Generation guns, period!
Colt used to letter them. According to the official Colt historian, Paul, on the Colt Archives, quote:
"We do not letter these guns - I believe that we used to, but we do not maintain any of the shipping records, so I think we stopped doing that.
As far as our position, it isn't really a position. The fact is the guns were produced under a licensing agreement with Colt Blackpowder Arms, manufactured to Colt's specifications. Now, does that make it a true Colt or not? I'm sure that debate will never have any consensus. My personal take is that they are not true Colt's, but that they do hold their own place within Colt collecting. Comparable situations would be the Argentine contract 1911's (not the Colt produced ones - the Argentinian produced ones), the Norwegian contract 1911's, the Spanish produced .25 autos, and the current Walther produced .22's."