You can't tell. The serial number only tells you when the frame was built not even when it was assembled into a bike. There are differences in the frames and examples of this would a bike that came with a 3 speed hub would have a hole in the rear bridge and fork to mount brakes. Where the tire goes past the seat stays for example is wider on balloon tired cantilever frames than on middle weight cantilever frames. Tabs for the chain guards might be different as would tabs to mount tanks but as i first said you can't tell the difference between a Jaguar vs Corvette vs 3 speed Tiger except by the paint. Schwinn was making bikes for kids not future collectable Mustangs or Corvettes so they did not care. Roger