"Jay Leno's Garage" has featured a wide variety of cars, but this 1923 McFarlan Model 154 Knickerbocker Cabriolet is truly one of a kind.

The car is part of California's Nethercutt Collection, and Vice President Cameron Richards believes it's the only surviving example.

Originally based in Connersville, Indiana, McFarlan was a carriage builder that moved into car production, but it focused more on luxury than volume, building only 600 cars per year between 1910 and 1928.

McFarlan didn't do things in half measures. The Model 154 weighs 5,200 pounds and, behind its Rolls-Royce-like grille, sits a 572-cubic-inch inline-6 with 18 spark plugs and four valves per cylinder. Those valves are arrayed on either side of the combustion chambers in a T-head arrangement, which was preferred at the time because of low quality gasoline, Leno explains in the video. The T-head eased cooling, lessening the chance of detonation.

All of those valves and spark plugs generated 120 hp, which is channeled to the rear wheels through a 3-speed manual transmission with a modern H-pattern shifter.

This car was owned by Roscoe Conkling "Fatty" Arbuckle, a famous comedian in the period, and sports a fold-out canopy and director's chair so the star could relax during rest stops. The driver was less fortunate. Arbuckle's Model 154 has a popular body style for the period, with a covered rear compartment but an open cockpit.

While forgotten today, the McFarlan was once considered an American rival to Rolls-Royce, Richards notes. Leno agrees with that, comparing the car from Indiana to a Rolls-Royce Silver Ghost. Unlike Rolls-Royce though, McFarlan didn't survive. The firm went bankrupt and was eventually bought by Auburn, another ill-fated Indiana automaker.