It's summer time and that means it's the best time of the year for many private car shows. And the Portland Art Museum is taking full advantage of this. As a part of its Allure of the Automobile Exhibit, they will have on display 16 of the world's most luxurious and rare cars from the 1930s through the 60s. One of those is the Mercedes 540 K Special Roadster, of which only 26 were built.

It was designed to be the most dominant on the road and built to very high standards by the automaker's then in-house coachworks Mercedes-Benz Karosserie in Sindelfingen. It's powered by a 5.4-liter engine that produces 180hp. It has a crankshaft driven Roots-type supercharger that adds an additional 65hp. The roadster has a top speed of 105 mph, despite its 5,500 pound curb weight. The second rare Mercedes-Benz on display is the iconic 300SLR; similar to the model driven by one Sir Stirling Moss at the 1955 Mille Miglia in Italy (he won).

It features a lightweight space frame and bodywork that's made from magnesium alloy. It's powered by a V8 with 310hp that also demonstrated mechanical fuel injection, something very advanced for the era. The exhibit will run from June 11 through September 11, 2011 at the Portland Art Museum. And in related news, RM Auctions will have a rare 1937 Mercedes-Benz 540K on the auction block at Pebble Beach this August. A similar 540K fetched $8.2 million back in 2007. This one is expected to bring in a new record price.