With a little over 4,000 examples made, the second-gen Ford GT is hardly what you’d call “common” – but it’s not uncommon to find them coming up for sale. The GTX1, though, is a very different story. That’s what makes this such a rare opportunity. And its unique livery makes it all the more so.

Following the concept showcased at SEMA in 2005, Ford contracted the convertible-conversion specialists at the Genaddi Design Group to build 30 examples of the GTX1 roadster – based on the retro super-coupe but with a T-top evocative of the GT40 in which Ken Miles and Lloyd Ruby won the 1966 Sebring 12-hour endurance race.

Apart from the open cockpit, the GTX1 was otherwise mechanically identical to the Ford GT on which it was based, right down to the 5.4-liter supercharged V8 that sent its 550 horsepower (410 kW) and 500 lb-ft (678 Nm) of torque to the rear wheels through a six-speed manual gearbox.

Only one of those 30 is known to have been done up in Hertz-style black and gold livery, and that’s the one you see here. It’s the 24th example made, and also features smoked headlights and the signatures of no less prominent figures than Carroll Shelby, Roger Penske, Henry Ford III, Edsel Ford, Dan Gurney, Tony Kanaan, and both Mario and Michael Andretti. It also just so happens to be one of only three fitted with the larger luggage compartment, making it just a little more usable as a daily driver or for long(er) road trips.

With all those elements in place, this GTX1 is bound to attract its share of attention in Monterey next month when Mecum Auctions sells it off to the highest bidder. Given how rare it is to see examples of the GTX1 come up for sale, we couldn’t tell you how much it might go for. Mecum’s never handled one before (as best we can tell), but RM sold one three years back for $330k, and the the last one we saw for sale carried an asking price in excess of half a million dollars.