The FCC recently approved the Nokia RM-877 that is compatible with AT&T's LTE bands, pentaband HSPA+/WCDMA and quad-band GSM/Edge. The FCC documents also not the device has NFC, Bluetooth and dual-band Wi-Fi.
Beyond that, there's not much more to go on but there is a strong possibility that this is the EOS Windows Phone aka 'Elvis' for AT&T. Nokia has requested all the juicy documents that have device photos, schematics, the user manual and device specifications to remain private. So for now, it's pure speculation that the RM-877 and the EOS are one in the same.