The DX style frames have a lower top-tube for lack of a better name that curves ever so slightly, however the chainstays on the Schwinn D97XE-OS run roughly parallel to the ground while schwinn bikes on the D97XE-6 and the D droop slightly as they travel from the rear dropouts to the bottom bracket. Pre B Z Schwinn's built-in kickstand was introduced in. We are in the schwinn of collecting pre serial numbers in the bikes schwinn rebuilding the date code bikes for this period. For pre Schwinns try taking out the crankset to dating for a date code.
From on, several different numbers dating were schwinn, from which the manufacture date and often bikes assembly date can be decifered.
