+1 on wrk101, but for a different reason, also.
For a few years, Trek would use one frame for 2-3 models, just change the model number based on component levels.
Centurion did this with the Ironman from 1987 to 1989, and Diamondback followed with the same protocol in the early 90's.
It appears Schwinn was doing the same thing with some of theirs, too, notably the Series Paramouns and PDG Aluminums.
I'm not sure about the 1420, but the 1450 and 2000, in one of those years, differed only in color and components.