I think I remember reading somewhere that it was every 7 years?
1939
1946
1953
1960
Edited to add: I went looking for the 7 year thing and found this: "Burdick issued a 20-page supplement in July 1940, and smaller supplements in October 1941, and October 1942, but with the war going on, another catalog didn’t come out until 1946, thus starting the every seven-year sequence."
Last edited by ZachS; 05-13-2014 at 03:01 PM.
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