MeeGo software while sporting a bold Nokia logo front and center on its shell. This mysterious slate has cropped up over at the mobile-review forums, where amateur sleuthing has already noted that the landscape centering of the Nokia logo is atypical -- both the N97 and N900 have it off-center -- which may well suggest this is a landscape-centric tablet first and a phone second (if at all!). Assuming the brand name imprint is the same size as on the N8 (Nokia loves to standardize those), we could be looking at a 4.5-inch screen on what is either an internal test device, or, more optimistically, a prototype for actual hardware. It's worth noting that the MeeGo seen on board is of the stock variety, whereas Nokia intends to ship its new flagship device(s) with an as-yet-unseen set of UI customizations collectively known as Harmattan. So we're certainly not looking at anything close to a final hardware / software pairing, but we are looking at something.
[Thanks to everyone who sent this in]