Windows 8/6.2.8400.0.winmain win8rc.120518-1423
This build was leaked to a Chinese file sharing website a few days before the official release, however, it was in Simplified Chinese and several files in the install.wim were corrupt.
This build was shown at Computex 2012 on an Asus Taichi notebook/tablet convertible. It was shown as being the Enterprise SKU and it also showed off a new activation reminder.
This build was also shown on MSDN Channel 9 - Developing for Windows on ARM.