Opportunities to buy an original example of the revered Porsche 911 Carrera RSR don't happen very often, but when they do they typically fetch for seven-figure price tags - and this pristine example is no exception. Listed for sale by RM Sotheby's is a 1973 Porsche 911 Carrera RSR 2.8, arguably the most iconic 911 racer of all time, that can be yours if you can afford the astronomical €1,695,000 asking price - that's around $2 million. But what makes the 911 RSR 2.8 so special to justify the asking price?

The introduction of the road-going lightweight 911 Carrera 2.7 RS allowed Porsche to homologate the 2.8 RSR for GT car endurance racing under FIA Group IV regulations.

Porsche's flat-six engine was extensively reworked with four-bearing racing cams, high compression pistons and twin-spark cylinder heads with bigger valves. As a result, the power output increased from 210 hp in the 2.7 to 300 hp in the 2.8 RSR. To compensate for the extra power, larger 917-type brakes were fitted and the wheel arches were extended to make room for grippier nine-inch wheels at the front and 11-inch wheels at the back. While the 2.7 RS was already as light as a feather, the 2.8 RSR weighs just 1,851 pounds thanks to weight-saving measures such as Perspex glass, a lighter flywheel, and a smaller cooling fan.

This is even more impressive when you consider that Porsche had to strengthen the chassis to allow the car to cope with the demands of endurance racing.

Out on the track, the RSR 2.8 secured overall victories at the 1973 Daytona 24 Hours, Sebring 12 and the Targa Florio, proving the 911 could be a successful track racer. Only 49 RSR 2.8 cars were delivered to privateers, and this is one of the earliest examples.

This particular car won races around the Caribbean and the US and was brought up to 3.0 RSR-specification for its final race at the 1975 Sebring 12 Hours with its first owner. Since then, it's had five owners and received a full restoration to its original track specification by its current owner in 2013. That means its original 2.8-liter flat-six has been swapped back, but RM Sotheby's will also sell you the 3.0 RSR engine if you have any spare change left.