With Smart city cars populating downtown streets in cities around the world, there might not be very much that's rare about Daimler's smallest product. But in 2002, the company unveiled the Crossblade. What might have otherwise remained a concept car was actually put into production, despite having no windshield, roof or even real doors to speak of. What it offered instead was a unique take on open-air motoring. It weighed only 1,600 lbs and its 600cc engine was tuned by Brabus to 71 horsepower.

That may not seem like much, but represented a significant bump over the base model's 50 or 61 hp engines. The vehicle remained a rare bird of sorts, but Robbie Williams bought one, prompting a marketing deal that had the pop singer promoting the brand. Now, as Smart prepares to roll out an all-new model, one of the original Crossblades is going up for auction. It will cross the block in about a month from now in London. The question is how much a collector might be willing to pay to own a rare but rather useless city car. (Photos by Simon Clay, Courtesy of RM Auctions.)