Gizmodo reports: This one caught us by surprise, but it comes from a source that has always been 100% reliable: Not only Apple may be working on a 10-inch tablet, but also in 13″ and 15″ models, one running Mac OS X. This source claims that the two touchscreen prototypes—made of aluminum, but on the shape of big iPhones—were in a factory in Shenzuen, China. One of them “was running Mac OS X 10.5.” When I asked, the source didn’t know if these were built for demonstration purposes, or if they were preproduction units. The company has a tight relation with Apple but “it’s not FoxConn.” As I said before, with everyone focused on the 10-inch tablet with iPhone OS, this sighting is quite surprising. It is possible that Apple may be just exploring other form factors, and these two models may or may not end being future products.

According to rumors, Apple is in the final stages of developing the Apple Tablet, a 10-inch tablet allegedly running the iPhone OS. Several sources claim that Steve Jobs—back in Campus—is now personally driving this project. However, until now there has been no reliable rumors on 13″ and 15″ models, much less one running full Mac OS X.