Marcus Hilman of Huntington Woods, MI wrote: "I have an old Campagnolo Gran Sport rear derailleur. It is chrome plated bronze. I know almost nothing about these, but my sense is that they developed very rapidly in the 50s, sometimes changing within a single year. Is there a resource for understanding the evolution of these derailleurs? I found John Siemsen's Pave album in Wool Jersey, but that doesn't document the history of the derailleurs."
Marcus, I don't know if it helps but below is an incomplete timeline of
Campy derailleur history;
1946 Corsa & Super 1949 Gran Sport 1951 Cambio Corsa, Tipo Paris-Roubaix, Gran Sport 1952 Gran Sport Extra, Sport 1961 Sportman 1963 Record 1964 Valentino 1967 Valentino Super, Nuovo Sport, Nuovo Record 1968 Valentino Extra, Sport Extra 1970 Gran Turismo 1971 Velox 1973 (End of Record) 1974 Rally, Super Record, Nuovo Gran Sport 1982 Gran Sport Rally 1985 C(Corsa)-Record 1987 (End of Super Record) Some are labeled as "low cost" but otherwise no indication of performance ranking. Hope this helps some.
Skip Magnuson
Spokane, WA
USA