There's been hints of it coming as early as February, but we now have a smoking gun at the FCC: the Galaxy S III is coming to T-Mobile. A Samsung SGH-T999 has popped up at the agency sporting newly added 1,700MHz AWS support that's the telltale sign of a T-Mobile device, along with the T999 name itself (the T989 is the network's Galaxy S II). It also totes 850MHz and 1,900MHz WCDMA bands being used for HSPA+ data rather than just voice, a clue that the phone is ready for refarmed GSM spectrum. Just in case there was any remaining doubt, we've further spotted a related T999V entry at the Bluetooth SIG with a rather familiar-looking image as well as a Samsung-hosted T999 user agent profile on the web that matches what we know about the Android 4.0 hardware. We have yet to get a look at whether or not the T-Mobile version is any different on the outside, but with the FCC's help, there's not much left to know before the expected summer US launch.