Hi Gregory,
The original Giant Step pedals came with 3 interchangeable plastic cams that created different chain/belt paths, kind of like DW's Accelerator eccentric sprocket versus the original Turbo concentric sprocket.
The story is that Pearl Drum Company already had dibs on the interchangeable cam design, and successfully (in court or out, I don't know) forced Sonor to remove them from the marketplace.
It would probably be cool to find one of those pedals in a sealed package, just so you'd get all the goodies. I would only buy a NOS double now. It really sucked when I got the pedal that was missing a cam, both chains, the other cams, and the belts that were installed on it were both split. Even if it had both cams, it wouldn't have had all the options as intended from the factory.
Between my GS Double, a pair of Sonor 5000s, an Axis A double, and a slew of Sonor Protech pedals, my pedal needs are now covered. I can't see myself spending any more money on bass drum pedals.
Brian