This is no ordinary Mercedes-Benz SL-Class. Although it may look like your typical R129-gen car from the late 1990s, it’s actually rarer than a Pagani Zonda supercar. That’s because this specific SL on sale courtesy of RM Sotheby’s is one of only 85 AMG-modified SL 73s in existence—basically a top-specification V12 SL 600 done up by AMG itself.

Built between 1995 and 2001, the R129 SL 73 is essentially the precursor to the modern-day SL 65 AMG. Engineers took the already-potent 6.0-liter V12 from the SL 600, bumped its displacement to 7.3-liters and modified its technical workings to produce a whopping 525 horsepower and 553 pound-feet of torque. To this day, the SL 73 features the largest displacement V12 ever fitted to any road-going Mercedes-Benz.