My first thought was "re-war/post-war" but it seems there is some overlap? Obviously there are differences in tanks, lights, etc., but frame, geometry, wheels, etc? Other pertinent differences? I was sure I would run across a model list somewhere that went something like "The Schwinn DX was manufactured from 193X to 194X in 24 and 26 inch sizes and was the top end offering.....for 1937 it came in....featuring......" but not finding anything like that online at least.
Then there's autocycle, motorbike....
Then there's autocycle, motorbike....