Apple gained a patent for a "portable display device" that seems to be for the original iPad, and seems likely to be a tool to help win future patent-infringement cases.
The patent application was filed in 2010, just before the iPad unveiling, according to Engadget. The patent also cites references for the device from 1947 until 2009 and includes all sorts of "elements that transpired between the filing and the granted date."
The reason? Likely because Apple's ongoing legal battle with Samsung will likely be bolstered by the U.S. Patent and Trademark Office's documentation. It will be a great piece of evidence in any new hearing, especially if Apple intends on stating its entire iPad design is original rather than just its parts.