This Mercedes SL 73 AMG is one of the rarest AMG variants ever to exist, signifying the absolute best money could buy at the time.

It is estimated that AMG built between 40 and 50 examples of the SL 73 from 1997 to 2001, so exclusivity is on par with the best in that field. This is a 1999 facelifted example that was delivered new in Japan and it shows just under 35,000 km (21,700 miles) on the odometer.

In order to turn this beautiful R129 into an SL 73, AMG took the 6.0-liter M120 V12 engine and enlarged it to 7.3 liters and adding upgraded internals. The end result is a rather very healthy 525 HP and 553 lb-ft (750 Nm) of torque. The fact that it shares its engine with the Pagani Zonda makes it even cooler.

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Performance is quite strong as you might expect, with the SL 73 AMG able to reach over 200 mph (322 km/h) flat out, once the 155 mph top speed limiter is removed. 0-60 mph is ‘traction limited’ to 4.6 seconds. AMG also made some necessary upgrades to the active suspension and braking system in order for the SL to keep up with the power.

The exterior differences are really subtle, making the SL 73 AMG one of the most undercover performers out there; AMG’s discreet bodykit compliments the elegant body lines, as does the set of the classic five-spoke alloy wheels. A twin exhaust and small exterior badging are the only giveaways that this SL packs some serious punch, while the cabin features the optional ergonomic seats dressed in black leather and the extended leather dashboard and door cards.

Overall, this SL 73 AMG is one of the finest modern classics available today, not to mention its exclusivity. Interested parties, head to RM Sotheby’s London auction on October 24 and place their bid.