Like any production car, there's a prototype that comes first. And if that car was intended to be special from the get-go, its prototype form has the potential to be worth a lot one day. That's exactly the case for the very first 1966 Shelby GT350 pre-production prototype. Set to go up for auction at Barrett-Jackson's Scottsdale, Arizona event in January, this GT350 prototype, chassis #SFM6S001, is already documented in the SAAC Shelby American World Registry, as primarily used as a test car during the development program over 50 years ago.

And yes, your eyes aren't deceiving you; it has a blue vinyl roof. Shelby and crew experimented with a vinyl roof back in '66 but ended up deciding against it for production. Another interesting feature is the Pony upholstery, an upscale factory option available with regular Mustangs, and this is the only GT350 to originally come equipped with it. Other notable features include aluminum inside rear-quarter trim and fittings for the rear-brake cooling ductwork. Power, of course, comes courtesy of the 289 ci V8, linked to a four-speed manual. This GT350 was also shown by Shelby American and even depicted in brochures and other marketing materials. In short, it served as a demo car until it was sold in 1968.

In 2011 it received a full restoration and has only been driven sparingly since. Barrett-Jackson doesn't provide an estimated price range, but based on previous fully restored and authenticated 1966 GT350s, we wouldn't be surprised to see this go for around a cool $500,000. Photos courtesy of Barrett-Jackson.