I think Schwinn was making them solely throughout that period. Later ones (late fities to early sixties) are sometimes rebadged Murray Fleetlines/Flightliners. Some of that later period are rebadged Huffies with similar styling.
crummy cl photos! rear triangle looks prewar schwinn but i can't tell. looks like a 40-41 dx but with a seat binder bolt through the stays instead of up on a collar (?) can't really see the dropouts....oh well, find out next week maybe.....