This 1968 Lotus 56 is being offered for Auction at the Motostalgia Brickyard Auction event that is running on June 12, 2015.

From the lot info for this 60s Lotus Indy Race Car for sale:

From Wikipedia:

The Lotus 56 used a modified version of the ST6 gas turbine used on the STP-Paxton Turbocar (“Silent Sam”) that almost won in 1967. The ST6 was based on a small aircraft engine that would become one of the most popular turboprop aircraft engines in history. But the car itself was an entirely new and more advanced design which introduced a distinctive aerodynamic wedge-shaped body rather than a cigar-shape, just a few years before the introduction of front and rear wings. USAC, the governing body of the Indy 500, had implemented new rules aimed at handicapping turbine powered racing cars by drastically reducing the air intake size. The Lotus 56 made up for reduced power with a sophisticated suspension design, retaining the 4 wheel drive concept of the Silent Sam, but with lighter weight, and advanced aerodynamics.

Lotus had suffered the death of Lotus’ ace driver Jim Clark in a Formula 2 race in Germany. Mike Spence was killed at Indianapolis while testing one of four 56s built. The remaining three cars with Graham Hill, Joe Leonard, and Art Pollard were entered for the race, with Leonard claiming pole position. Unlike the year before, when the STP-Paxton Turbocar easily outperformed the other cars in the race, in the race the turbine cars were relatively evenly matched with the other top contenders, much of which must be attributed to aerodynamics and chassis design and not to the turbine engine. Hill’s car crashed, Pollard’s car broke down, while Leonard was leading with just a handful of laps to go when the a fuel pump shaft failed. Shortly thereafter, the USAC imposed additional restrictions on turbine cars that essentially removed them from competition. For the second year in a row STP turbine cars had brought innovation to the Indy 500 and had failed to win while leading within a few laps of the end of the race. USAC subsequently banned turbine cars and four-wheel drive completely, but it was unusual enough that Mattel produced as model as the “Lotus Turbine” as one of the popular mass-produced die cast Hot Wheels cars.

In 1971 the Lotus 56 was raced in Formula 1 on occasion by Team Lotus but the large fuel tanks required to allow it to run an entire race without refueling left it overweight and uncompetitive.

The Lotus 56, while never winning a race, demonstrated the importance of aerodynamics in racing cars, along with Jim Hall’s Chaparrals, and effectively set the mold for open wheeled racing cars for the next ten years. Chapman’s Lotus 72 employed the same wedge nose shape and went on to win three world championships in Formula 1.