Bruce Weiner made a fortune in the candy business, and now he's selling off his automotive Skittles.

Mr. Weiner's taste-the-rainbow collection of 200 microcars goes up for auction Friday and next Saturday in Madison, Ga., in a 25,000-square-foot museum devoted to the cars' Lilliputian strangeness and ingenuity.

Dan Neil on Microcars

RM auctions will hold the sale of Isettas, Messerschmitts and many others in Madison, Ga. RM Auctions

The Atlanta-based entrepreneur has collected antique firearms, watches, and what's likely the world's most authoritative survey of chewing gum (he once owned Fleer Confections, the inventors of Dubble Bubble gum). He's also had his fair share of Ferraris. But nothing has held his interest like microcars.

"Acquiring seven-figure collector cars is purely a function of money," said Mr. Weiner. "Collecting microcars is about the hunt, finding the best of what's out there and chasing it down." RM Auctions hopes to raise $6.1 million to $8.1 million in total.

The radical minimalism of these machines, built mostly in Europe in the 1950s and early '60s, reflected the region's postwar scarcity. (One resourceful builder beat old cooking pots into fender panels.) They typically measure 10 feet long or less, with less than 700-cc engine displacement and one or two seats—arranged side by side or in tandem, scooter style. The cars' tenure didn't last long: Europe's economic miracle was under way and more comfortable cars grew more affordable. By the time of the zanily bubblelicious 1966 Peel Trident, it was over.

In their time, microcars were utterly disposable. The collection's specimens —most with a shiny candy coating courtesy of the museum's restoration shop—owe something of their survival just to being adorable. "Due to their small size, toylike appearance and their abundance of character, microcars tended not to be scrapped so much as put away," writes Peter Svilans, the museum's former curator, in the catalog essay. Among the oldest cars is the golf-cart-like 1949 Voisin Biscooter prototype, with a skin of gleaming riveted aircraft aluminum, a cuirass worthy of a Fritz Lang ingénue.

The most familiar of these machines are the Messerschmitt KR 200 (Kabinenroller) and the BMW BMW.XE -1.40% Bayerische Motoren Werke AG Germany: Xetra 91.42 -1.30 -1.40% July 10, 2014 5:35 pm Volume (Delayed 15m) : 1.47M P/E Ratio 10.96 Market Cap €59.65 Billion Dividend Yield 2.84% Rev. per Employee €695,481 07/10/14 Vonnegut: When It's Time to Di... 07/10/14 VW Adds Luxury for the Common ... 07/08/14 Palladium Prices Rise to 13-Ye... More quote details and news » Isetta, both products of former aviation firms in Germany forbidden from building aircraft. Plane builders from both sides of the war—like Ernst Heinkel, Enrico Piaggio and Gabriel Voisin—were "presented with an entirely new set of sobering, restrictive, ground-based parameters" for their postwar duties, writes Mr. Svilans.

Their aircraft experience led to the use of lightweight tubular structures called space frames and large, blisterlike canopies made of Plexiglas (thus the category of "bubble cars"). Likewise, their commitment to streamlining created cars that even now seem startlingly futuristic. The 1956 Paul Vallée Chantecler looks like a one-man submersible to explore off-world oceans.

The Isetta, designed by Italy's Iso Rivolta company in the early 1950s, became the most successful single-cylinder car in history. Built by licensees in several countries (most notably, by BMW in Munich) the instantly recognizable Isetta has a marvelously effective design in which the entire front panel of the car—including steering wheel, console and windshield—swings on a set of side-mounted hinges. It's like opening a refrigerator door and climbing in. Fans of the movie "Cars" will remember that the little Italian tire-changer, Luigi, is an Isetta, and Fred Astaire and Audrey Hepburn squeeze into one in the 1957 musical "Funny Face."

There were dozens of others: Goggomobile, Fulda and Bond. Many were brilliant. The Zundapp Janus was a double-ended microcar in which passengers, like the Roman God, faced both ways. The seats could fold flat into a bed—this at a time when Europeans loved cheap caravanning.

Not all of Mr. Weiner's cars are so nobly framed, of course. Some are gawky, silly, and look somehow incomplete without clowns tumbling out of them. Others represent genuinely bad engineering ideas. Parked in direct sunlight, the poorly ventilated bubble-top Peel Trident could probably cook a chicken in about an hour. And yet, these cars paint a remarkable picture of a time when Europe was desperately lacking in everything but talent.

"It tells me that it doesn't matter how devastated your society is," said Mr. Weiner. "You can always get back on your feet."