For dedicated Willys-Knight collectors, this one lives at the top of the list: the 1929-30 66B Plaidside Roadster.

Among its various accomplishments, Willys-Overland, Incorporated of Toledo, Ohio was the leading producer of vehicles powered by Knight twin sleeve-valve engines in the USA, if not the world. Beginning in 1914, the automaker produced Willys-Knights in four and six-cylinder versions (and even a V8, briefly) and by the mid-’20s, the engines had achieved a refnined state of development. For 1929, the Willys-Knight was offered in three new models: the 45 hp 56A, the 55 hp 70B, and the top-of-the-line 66B with 72 hp. While the Willys-Knights sold in smaller numbers than the conventional Willys and Overland models, they were the company’s flagship cars.

Priced solidly in the Buick class, the big six-cylinder Willys-Knights were known for their  utterly smooth and quiet engines (earning the nickname “silent Knight”) and for their handsome but conservative styling—most often in roomy and comfortable four-door sedans. But in January of 1929 at the Grand Central Palace in midtown Manhattan for the New York National Automobile Show, Willys-Overland flipped the script, introducing the glamorous Plaidside Roadster.

The Plaidside name was inspired by the distinctive pinstripe motif, created by Amos Northup, on the doors and body sides. Along with his distinguished career as an independent stylist, Northup also briefly served as chief of design at Willys-Overland. (See our feature here.) He is credited with the body design as well as the unique paint scheme. However, the bodies were constructed by the Griswold Motor Body Company on Commonwealth Street in Detroit. Although the company is littlle known today, it supplied bodies for Jordan, Chrysler, and Graham-Paige, while Griswold also did the 1929 Auburn Cabin Speedster designed by Alan Leamy for E.L. Cord.

Though estimates vary, it’s said that around 400 Plaidsides were produced in 1929-30, but reportedly, only 13 are known to survive today. Their rarity no doubt contributes to their desirability and to their informal status as the ultimate Willys-Knight. They don’t change hands often, but when they do they can command prices in the low six fgures, an amount few other Willys-Knights, if any, can begin to match. While the most familiar color scheme is Hunter Green with Harper Green fenders, other combinations were also available.

There was a Plaidside four-door Phaeton, too, but here the W-O experts say only three were actually produced and just one is still in existence. While the Plaidsides were a high point in the Willys-Knight story, they came nearly at the end. By 1930 the company was already in financial trouble, the Knight patents would soon expire, and there would be only two more Willys-Knight models, the 66D and 66E, before Willys-Overland went bankrupt. After emerging from reorganization in 1933, the company built only trucks and small cars for the rest of the decade.