The model year of a Schwinn bike produced in 1948 or later can be determined by locating the bike's serial number and comparing it to a serial number and date chart. Serial number information from before 1948 was lost in a factory fire and is extremely sparse.
Schwinn serial numbers may be found in several different places on the bike. Most bikes from the 1960s are stamped with the serial number next to the spot where the rear wheel axle connects with the frame. Starting in the 1970s, many bikes were manufactured with the serial number on the Schwinn seal, located somewhere on the bike's frame.