A senior member on XDA forums voteccow, informs that he just bought a AT&T branded HTC One X phone from eBay which apparently is a test/development unit.
After receiving the unit in his mail for his surprise he found out that the phone had all sorts of particularly interesting markings.
“It has the AT&T branding on the top and when I boot up the phone it says “This build is for development purposes only,” said voteccow in a post on XDA.
He also provided several screenshots with the AT&T HTC One X smartphone, plus a couple of bootloader shots as well.
source XDA Forums