The LG C900 has been outed by a Bluetooth SIG filing as having a September 28th launch date here in the U.S. The C900, which will be released by carrier AT&T, is a Windows Phone 7 full-QWERTY slider device that will be LG’s first swing at a WP7 handset. The handset will also be released internationally as the C900B, C900K, and C900N. The device certainly has been making the rounds in the last few days. We were dropped a tip of the devices existence, shortly after Engadget was sent an image (seen above), and now this Bluetooth SIG filing has been released. What do you think? Does the September 28th date hold water?