Schwinn changed the rear derailleur on the P15-9 from the Campy Gran Turismo to the Schwinn-Approved Le Tour GT-300 (rebranded Shimano Crane) in late 1972 because the Gran Turismo was a POS and Campy didn't have a decent long cage RD at the time. Schwinn used the GT-300 on the P15-9 until at least 1978.

The bar-end shifters on my 1972 P15-9 are Campagnolo, but the SunTour shifters work much better and may have been supplied on some units.

At $300, it's a helluva deal.