Back in the day, it was required to memorize all significant and insignificant measurements for the previous ten years. Since bicycle dimensions changed very rarely, this is actually quite easy.
(Just kidding. But I spent my lunch breaks at the old shop studying catalogs and the Schwinn repair manuals.)
The Japanese bikes of the early '70's tended to use only one or two different sets of lugs. Because the relative angles of the tubes didn't vary much, top tubes of large frames tended to be quite short.
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Jeff Wills
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