With aircraft you have the "first" designation such as C-130 and then you will have changes after that model that denotes the "new" aircraft such as the C-130A. My uncle died last week and I remembered his having worked on IIRC the C-133. According to him the C-133 had so many problems they were constantly making changes/upgrades to the aircraft and actually ran through the entire alphabet! I have never verified that story but don't doubt it since the aircraft was not in service long like the C-130 that is still flying today. Did BMW do the same thing with the dashes? A search turned up nothing for me. Is there a resource on all of these? How important are they for someone interested in finding their first cheap Airhead that will ridden commuter style and not babied?