Mid-2007 Prototype MacBook Air Found on eBay
MacRumors forum member Brett33 bought an "as is" MacBook Air on eBay for a selling price of $730. As it turns out, it appears the machine is actually a prototype model of Apple's MacBook Air.
After receiving the unit, Brett33 noticed that the bottom of the laptop was made of black aluminum and that the screen bezel did not have "MacBook Air" written on it. The laptop runs an interim build of Mac OS X 10.5 (8R4016).
The serial number on the machine indicates that it was built in May 2007, over six months before the MacBook Air was introduced. Another poster was able to specify that this model represented "M82 PROTO2 ENC 4", based on the serial number.
Though rare, prototype Apple machines have been known to circulate.