One of the most desirable motorcycles ever built hits the block today, and you can expect bidding to reach well into six figures before the gavel falls.

A 1940 Brough Superior SS100 is among the crown jewels being auctioned during The Quail, A Motorsports Gathering. Yes, that's actually its name, and the super-exclusive annual bash attracts well-heeled petrolheads from around the world.

The 1940 Brough Superior SS100 (pictured) is a special machine indeed, one known in its day as the "Rolls Royce of motorcycles" because it so beautifully combined style and speed. The 998-cubic-inch engine was good for 45 horsepower, and every bike that left the factory in Nottingham, England was personally tested by George Brough to ensure it would do 100 mph.

The SS100 was a wickedly fast machine from a company with a rich and occasionally grisly history: T. E. Lawrence — who owned seven Brough Superiors — died while riding an SS100 in an accident that prompted wider use of helmets.

This particular motorcycle has a somewhat happier provenance, however, being the very last Brough to roll off the production line. It's expected to sell for $350,000 to $400,000.

Joining the Brough on the block is a 1954 AJS E95 "Porcupine," a machine built specifically and exclusively for grand prix racing. The bike earned its nickname because of the cooling fins on its cylinder head.

Mechanically, it was an improvement over its predecessor, the E90, but the 500cc machine never enjoyed the success of the earlier bike. It was plagued by finicky carbs and had a habit of killing magnetos. Still, it's a historically significant motorcycle and ultra-rare — AJS built just four of them. Auction house Bonhams expects bidding to reach $750,000.

Motorcyclists can't resist debating the greatest bikes of all time, so we'll kick start the conversation by listing nine bikes that join the SS100 in our fantasy garage of the world's most desirable motorcycles.

Photo: Bonhams