B.A.T. Alfa Trinity, some of the world's most famous concept cars, are up for auction

Of the cars that never saw production, there are a handful that nevertheless have had an outsized influence. Among the most famous are the wild Berlinetta Aerodynamica Technica (B.A.T.) concepts commissioned by Alfa Romeo in the mid-1950s. Three B.A.T. Alfas were created by Italy's Bertone design house and were unveiled at succeeding Turin auto shows in 1953, '54, and '55. The cars are now coming up for auction for the first time as a group at RM Sotheby's Contemporary Art Evening Auction in New York on October 28.

The first of the trio was B.A.T. 5, which like its successors was built on the Alfa 1900 Sprint production chassis. The goal of the B.A.T. 5 was aerodynamic efficiency, and the car boasted a cD of 0.23. Aiding the cause were covered front wheels, a greenhouse with steeply curved side glass, and twin tail fins.

The second concept was B.A.T. 7, from 1954. It has the wildest styling of the trio, with sharply curved tail fins. It also has the lowest drag coefficient, at 0.19.

B.A.T. 9, from 1955, was the most production-feasible of the group. It features an Alfa Romeo shield grille at the front and exposed headlights with clear covers.

All three are credited to Franco Scaglione, working with Nuccio Bertone. They were seen together for the first time at the 1989 Pebble Beach Concours d'Elegance. They would appear together again at Pebble Beach in 2005 and at Bertone's 80th-anniversary celebration in 1992. The cars were acquired by a single owner sometime after their first Pebble Beach appearance.

The ability to acquire all three at once is part of what makes this an extraordinary opportunity. The B.A.T. Alfas are being sold as a single lot and are expected to bring between $14 million and $20 million.