Jan Heine wrote:
> That was the first version of 1952. The 1951 versions are even
> rarer, and probably more expensive. The final, mass-produced
> version was introduced in 1953.
>
> There was an article on all these early Campagnolo Gran Sport
> derailleurs in Vintage Bicycle Quarterly Vol. 2, No. 2.
This version of the Gran Sport derailleur actually has a model name. It is in the 1952 Campagnolo catalog as a "Gran Sport Extra" (easily identified by the extended nose on the upper end of the outside pulley cage).
Olds posts about Gran Sport Extra in archives:
http://search.bikelist.org/
Chuck Schmidt
South Pasadena, Southern California
United States of America
http://www.velo-retro.com (reprints, t-shirts & timelines)