Well, I can narrow it down for you. I recently acquired a 1970 P-15 with an original Gran Tourismo, and another CR member sent me an image of a 1971 Schwinn catalog still listing the Gran Tourismo. I'm about 99% sure that by 1974 at least the P-15 was using the Crane GT, marked as Schwinn Approved GT 500 or such like. So I would be willing to wager the Crane GT first appeared on the P-15 in 1972 or 1973.
As to when the Gran Tourismo first appeared, I don't know. When was the P-15 introduced as a distinct model? If that was the mid-60's, then maybe the Gran Tourismo was the original P-15 RD. If the P-15 is older than that, I would guess it might have at one time used the Huret Allvit, as did my circa 1961 Schwinn Superior.
Regards,
Jerry Moos Big Spring,Texas, USA
gthies1@cox.net wrote: I'm sure someone here knows when the Campy Gran Tourismo was stock on Paramount P-15s and when it was dropped in favor of the Shimano Crane.
Greg Thies
Vienna, Virginia
USA