There is perhaps no single letter more regarded in the performance car world than BMW's M. But before it appeared on cars like the M3 and M5, it lent itself to the M1.

The M1 (designated E26 internally) was BMW's first mid-engined car. It was initially conceived to compete in Group 4 and Group 5 racing, which stipulated at least 400 cars be produced to homologate it for the purpose. The car was designed by Giorgetto Giugiaro and originally slated for production through a partnership with Lamborghini, though the deal fell through. Instead, the tubular chassis was built by Marchesi, Trasformazione Italiana Resina handled the fiberglass body, and final assembly was completed at the German convertible manufacturer Baur.

Production delays plagued the M1 and effectively ended any chance of having the cars ready to compete in Group 5. Instead, BMW created a one-make support series for the Formula One calendar called Procar, which would pair race-prepped M1s with retired F1 pilots. The series is but a footnote in the history of motorsport.

But what of the car itself? With just 455 produced from 1978 to 1981 (399 road cars, 56 race cars), the M1 remains one of the rarest BMWs ever built. It looks like no other BMW before or since, with the twin kidney bean grille its most distinctive BMW feature. Otherwise, the car's wedge lines were clean and simple, a departure from so many other mid-engined supercars of the era.

Power came from a mid-mounted, longitudinally aligned, 24-valve 3.5-liter inline-6 with Kugelfischer mechanical fuel injection. Power was delivered to the rear wheels through a 5-speed ZF gearbox. In street trim it was good for 277 hp and 243 ft-lb of torque, enough power to get the 3,200-lb car to 62 mph in 5.6 seconds on its way to a 162 mph top speed. This is the engine that would go on to power the first-generation M5 sedan.

In Procar guise (which shared most specs with Group 4), the M1 delivered 470 hp, while cars built to Group 5 specs utilized a smaller turbocharged 3.2-liter engine capable of 850 hp.

Suspension was independent all around, through coil springs and twin A-arms, while servo-assisted ventilated disc brakes with Bosch ABS took care of stopping needs. Overall, handling is quite neutral, with excellent grip from the 16-inch Pirelli P7 tires.

Road cars lacked nothing in creature comforts. Interiors were standard black and gray, with Recaro sport seats, air conditioning, power windows and mirrors, a three-spoke M steering wheel, and a heated rear window. Fit and finish throughout the car were in keeping with typical Teutonic attention to detail.

Yet another footnote in the M1 story is the "art car" created by pop artist Andy Warhol, whose Group 4 racer finished sixth overall at the 1979 24 Hours of Le Mans.

Though the M1 proved a short-lived experiment, the stir and commotion it caused in period have immortalized it in the eyes of enthusiasts, and today it remains a viable and alluring alternative to many of the contemporaries that came out of Italy during the same era.