The Schwinn Bicycle Co. is an American bicycle company and a bicycling history icon. From 1948 to 1982, Schwinn pioneered its own models of cruisers, touring bikes and three-speeds, fabricating their own frames and components in-house. After the "Bicycle Boom" of the 1970s, however, Schwinn's proprietary frame-building technology and heavier bikes became less economically viable in an increasingly weight-obsessed industry--resulting in millions of unique vintage and antique bikes that can be identified by their serial numbers. Dating these bikes is usually the first step toward proper appraisal of a vintage Schwinn machine.
Find the serial number. Upon production, all Schwinns had a serial number stamped in one of three places on the frame.
The first possible location is on the underside of the bottom bracket. Sheldon Brown's Bicycle Glossary defines the bottom bracket as "the part of the frame around which the pedal cranks revolve." Turn the bike upside down to view it better.
The second possible location of the serial number is on the left rear dropout--the "fork end that allows the rear wheel to be removed without derailing the chain first," according to Brown's Glossary. Look for the left dropout on the same side as the chain.
The last of the possible locations is on the head tube, which is are on the very front of the bicycle (between the handlebars and the fork) on which the Schwinn logo badge is affixed. Look below and to the left of the badge to find the serial number.
Visit the Schwinn Date Codes website--this is the "cheat sheet" for identifying Schwinn serial codes on the Internet, and it contains many other related resources and facts.
Follow the appropriate link. The Date Codes website has a link for each of the three places mentioned in Step 1 where you might have found the serial number. For example, if you found your code under the bottom bracket, click the link below the line on the website that says, "IF THE SERIAL NUMBERS ARE FOUND UNDER BOTTOM BRACKET."
Match your serial number and find out the exact year, month and day your Schwinn was made. For appraisal purposes, this date will be helpful in determining your bike's collector value, though it is not a definite rule. Generally, the value is determined by what those within the community of Schwinn collectors would pay for that specific model and year. Some models are rarer and would command more value than others. Research auction and collector websites for more information.