On Tuesday, after review by a patent examiner, the United States Patent and Trademark Office awarded Apple an additional design patent relating to the iPad's "ornamental" design. The ornamental design feature encapsulated in US Patent D670,286 for a "Portable display device" appears to be a literal rounded rectangle. But whether or not this patent would be useful against Apple's rival and alleged "copy cat" Samsung in court is unclear.

Apple had originally asserted design patent D504,889 against Samsung as part of its massive lawsuit alleging that Samsung copied Apple's iPhone and iPad devices to make its competing Galaxy S and Galaxy Tab devices. That design patent, filed in 2004 and awarded in 2005, appears to be based on an early iPad prototype.

US federal judge Lucy Koh had originally awarded Apple a preliminary injunction against Samsung's Galaxy Tab 10.1 device based on her judgement that Samsung likely infringed the '889 patent. However, a jury later ruled that the Samsung device did not infringe this particular patent, though Samsung had infringed several other patents in the process of designing various smartphones and tablets. Samsung noted that it was "unfortunate that patent law can be manipulated to give one company a monopoly over rectangles with rounded corners," and the injunction was later rescinded.

The '286 patent awarded on Tuesday appears to give Apple the exact patent the Samsung and Apple critics have erroneously claimed that the '889 patent was. The patent includes a number of drawings of the original iPad design, with most of its uniquely identifying features in dashed lines. As stated in the patent description, "broken lines in the Figures show portions of the portable display device which form no part of the claimed design."

The only unbroken line in all the figures is the outline of the flat, rounded rectangular front face of the device. All the other identifiable features, such as the speaker grille, round home button, display size, Dock connector, or even its curved back, are not covered by this design patent.

It's uncertain whether this patent on portable display devices with an overall rounded rectangle shape and flat front surface would be of any use to Apple in court. "This design patent gives Apple no new advantage, because no one is out there trying to market an iPad lookalike," Lea Shaver, Associate Professor at Indiana University's McKinney School of Law, told Wired.

However, the patent examiner for the '286 patent cites an exhaustive list of references in her research, including most of the devices Samsung considered prior art for Apple's earlier '889 patent. This includes various digital photo frames, the Knight Ridder tablet concept, and HP's early tablet PCs. Even with all the prior references, Apple's design element appears to have passed muster.

Shaver also apparently based her evaluation of the utility of the '286 patent on details that aren't considered part of the ornamental design, such as the home button shape and placement. "The Samsung Galaxy doesn't have a center bottom circle, it doesn't have a camera in the top center, and although its back panel slopes to meet the front, the angle of that slope is different," Shaver said. Some of those features, including is thin, flat bezel, screen size, and home button shape and position, are covered in a separate design patent (D627,777).