Hello pappymac.
I don't seem to have received a PM from you, but I know that the 4651X (The Banker shape) was first catalogued with the X for a saddle mouthpiece - I think this was in 1969-1970. I think that later on it became a 4651DC (in the 1975 catalogue). The Small Chubby Pot shape 149 was a simple saddle (X) in the 1970 catalogue and in the 1974 catalogue it appeared with a DC mouthpiece.
The 2615 relates to the group 2 shape no. 615 - The Shannon which is a slightly forward canted Dublin. This appears in the 1970 catalogue with a taper mouthpiece and with a DC in the 1974 catalogue. I have never seen the Shannon shape with a simple saddle fitted and stamped with an X. This could have been from the inception of the shape when they were 'playing with' the best mouthpiece to fit to this shape.
Whilst looking at the 1974 catalogue, I now realise that out of the thirty six catalogued shapes that Charatan made at this time (in various sizes), 35 are fitted with a DC mouthpiece!!! One is not.. which one? The Prince.
The 'L' stamp was stamped on pipes going to the USA from the factory. It served as a check for Herman Lane whether pipes that turned up for repair in New York were bought in the U.S. or in London (where they were cheaper).