From what we can tell, this is likely a phony casing with the Galaxy S III's internal hardware tucked inside. The device is running the latest version of Android, Ice Cream Sandwich, and has a single home button at the bottom. It also has the on-screen control buttons that are one of Android's new signature features.
We'll have all the official details on the Galaxy S III when Samsung unveils it to the press at an event in London on May 3.
For now, here's the photo: