Regarding Brook Watts' query: "I've been wondering when the use of top tube cable clips came along. ...I'm most curious about immediately after the war: 1945 through 1950-ish...."
A few types of metal brake cable clips in black enamelled spring steel or in aluminum are listed on page 35 of the 1939 Brown Brothers catalogue. I assume these were available in your later timeframe. Rubber brake cable clips were available as well.
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Peter Brueggeman
La Jolla California USA
4peebee(at)peterbrueggeman.com