An extremely desirable Porsche 911 race car went up for sale at an event coinciding with this past weekend's 2023 Goodwood Revival.

Listed by Bonhams, the car in question is a 1973 Porsche 911 Carrera RSR, one of the most iconic 911 race cars. It was offered via private sale so the results of the transaction are unknown. Bonhams has confirmed that the car did sell.

Known as R7, it's believed to be one of just three factory-backed examples surviving today. The highlight of its racing career was fourth place at the 1973 24 Hours of Le Mans—the best finish for an RSR at the French endurance race.

While still recognizably a 911, the RSR was heavily modified with widened fenders, a large rear spoiler nicknamed the Mary Stuart (after the Scottish monarch's signature collar), and an uprated 3.0-liter flat-6 engine. The changes were extensive enough that the RSR was classified as a prototype for the 1973 Le Mans race, according to the auction listing, which meant it competed against dedicated sports racers rather than production-based cars, making its finish all the more impressive.

1973 Porsche 911 Carrera RSR (photo via Bonhams)

1973 Porsche 911 Carrera RSR (photo via Bonhams)

Driven by Herbie Müller and Gijs van Lennep, and wearing the classic Martini racing livery, the car finished behind only a trio of prototypes from Matra-Simca (in first and third) and Ferrari (second). The car finished out the season with the factory team with races at the Österreichring and Watkins Glen.

R7 was then sold to Mexican race team owner Hector Rebaque, who brought it back to Le Mans in 1974, though it failed to finish that year due to ignition problems. In 1977, R7 was sold to Italian collector Massimo Balliva, who kept it hidden for almost 30 years. This led to rumors that R7 had been wrecked and parted out under Rebaque's ownership.

Balliva ended up sending R7 to France for a restoration around 2009 or 2010. He then sold the car to a U.S. collector. R7 then became the subject of a legal battle in U.S. courts over its identity, as another owner claimed a different car was the real R7. Porsche engineer and team manager Norbert Singer was brought in to identify the genuine article.

With its identity confirmed, Bonhams expected R7 to sell for between 3.7 million and 5.7 million British pounds—about $4.6 million to $7.1 million at current exchange rates. Even if it reached the higher estimate, it wouldn't be the most expensive Porsche sold in recent years. A 1970 917K prototype racer used in the Steve McQueen movie "Le Mans" sold for $14 million at a 2017 auction.