I noticed a difference between my old '49 The Martin alto and my later '54 model. The bore is different, it seems narrower on the later one, and the later one seems to have a different bow and bell shape. The necks are definitely different, since I interchanged them and easily noticed how much smaller the later neck was in terms of bore. Also the later one has been set up with lower key heights, but maybe that's just up to the preference of the tech. Has anyone else who has owned 2 of more of these horns from different vintages noticed differences?