June 14, 2007

    I have a 5-speed Schwinn DeLuxe Twinn
tandem. The only serial number I could find is on the junction of the front fork where it is marked G1815172. I know the G stands for July, but what is the year of manufacture?

Jerry H.

    From 1959 to 1964 Schwinn used a serial number format of one letter followed by a bunch of numbers. The letter stands for the month (with A = January) and the first number corresponds to the last digit of the year. So, for example, B900001 means they made the bike in February 1959. As you correctly guessed, G means they made your bike in July, and the following number means they made it in 1961.
    Apparently somebody at Schwinn thought they might run outta numbers, so in 1965 they went to a format of two letters followed by numbers. The first letter represents the month, and the second letter means the year (e.g., AA = January 1965, GB = July 1966). They skipped the letters I and O to avoid confusion.
    During high school in Chicago I worked next door to the Schwinn plant. Now I know why they had all those slide rules.

Mr Bike

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