Here's the page for Schwinn serial numbers:
http://www.angelfire.com/
C7021 doesn't correspond to any of the modern numbers.
Calvert Guthrie Kansas City
In a message dated 1/4/2002 9:39:44 PM Central Standard Time, stevens@veloworks.com writes:
> C7021 would make it the 21st frame built in March of 1970.
>
> Steven L. Sheffield