Nick Mason has held onto chassis 10R of the McLaren F1 GTR for 26 years. Mason purchased the car straight from McLaren in 1999, making him the sole private owner it has ever had. Now, RM Sotheby's is bringing it to Monterey this year with a valuation north of $35 million – making it one of the most significant collector car offerings in years.That figure demands some context, and the car earns every bit of it. Chassis 10R rolled out of McLaren's Woking facility in December 1995 as the very first F1 GTR built to the revised 1996 specification. The 1996 iteration of the car was engineered to compete directly against purpose-built factory entries such as the Porsche 911 GT1, representing a significant evolution beyond the 1995 model, which had claimed victory at Le Mans with little more than a road-going version of the car in modified form.For the 1996 model year, the GTR received a sharper front splitter, aerodynamic bodywork revisions aimed at boosting downforce, and a magnesium gearbox casing that cut the car's weight by 38 kilograms compared to its predecessor. Per Wikipedia, it also topped 330 km/h on the Mulsanne Straight in 1996 – quicker than the subsequent long-tail 1997 car and even the Porsche GT1. Only nine were ever built.Why Chassis 10R Stands Above the RestMcLaren retained 10R for internal development and promotional purposes instead of selling it to a privateer team, giving it the same status as chassis 01R – the car that claimed overall victory at Le Mans in 1995 while campaigned by Kokusai Kaihatsu Racing. Like 01R, it's a short-tail prototype, and it's one of just two such cars ever made. During the winter before the 1996 season, 10R was tested at Magny-Cours by works drivers including JJ Lehto, who had co-driven the Le Mans winner the previous year. It later traveled to La Sarthe for pre-qualifying under the Kokusai Kaihatsu banner with David Brabham at the wheel, finishing 8th in class before sister car 11R took the race entry instead.What genuinely separates it from every other GTR is the livery. No other F1 GTR left the factory wearing a designed livery – 10R ran in scarlet with yellow "96 GTR" graphics during its promotional duties, a look that's made it arguably the most recognizable F1 ever put on paper. That it ended up with the drummer of Pink Floyd – the band whose prism artwork for The Dark Side of the Moon became one of the most reproduced graphic images in human history – feels less like coincidence and more like the universe tidying up.AdvertisementAdvertisementMcLaren converted the car for road use before Mason registered it as "K40 MCL" in 1999, and the Lanzante family has maintained it ever since. Paul Lanzante, who managed the Kokusai Kaihatsu team to that famous 1995 win, handled early work on the car. His son Dean took over for subsequent restorations – including one prompted by a journalist putting the car into a wheat field during a 2009 test drive, and another after Mason clipped a tire wall during a 2017 demonstration at Goodwood. According to RM Sotheby's, Mason placed no spending limits on the car's upkeep, sending it back to Lanzante for servicing following each significant use. A recent Lanzante inspection report will accompany the car at auction.Mason's collection – which spans a Ferrari 250 GTO, Bugatti Type 35, Jaguar D-Type, Maserati 250F, and Porsche 962, among others – isn't the kind assembled for show. That 10R lived in it for a quarter century, saw regular use at events like the Goodwood Festival of Speed and two 106 Drivers Club tours, and was still being properly maintained and driven, says something about how the car was treated.A 1994 McLaren F1 in LM specification sold for just below $19.8 million through RM Sotheby's at its Monterey sale in 2019, according to the auction house's records. Earlier this year, a road-legal GTR changed hands for $25.3 million in Abu Dhabi, according to Carscoops. The $35 million-plus valuation placed on 10R stems from a combination of factors that set it apart from comparable examples: its original factory livery, prototype designation, unbroken single-owner history, and 26 years of maintenance carried out by McLaren's own specialists. Gordon Murray once said, per the RM Sotheby's listing, that "winning Le Mans at the first time of asking was harder than winning back-to-back Formula 1 Championships."The car being offered at Monterey is as close as you can get to holding that achievement in your hands.