Unfortunately, this being similar to the international model, the LTE bands it supports are 1, 3, 7, 8, 20 (800, 900, 1800, 2100, 2600Mhz). This means that if you get this version of the phone, you might experience some problems with AT&T's LTE network, which currently runs on bands 2, 4, 5, 7, 17 (700, 850, 1700, 1900, 2600MHz), meaning that you might lose LTE coverage in some areas. The same applies to T-Mobile, because they use the 1700MHz and 2100MHz bands for their LTE and HSPA+ networks, and this version of the device supports only the 2100MHz band. Apart from these issues this Lumia 1520 variation, featured at Expansys USA, still sports a gorgeous 1080p 6-inch IPS LCD display, 20MP back snapper and the Snapdragon 800 SoC.
Expansys USA are currently selling the unlocked version of the Lumia 1520 for $799.99. It looks like they only have the device in yellow. Still, if you want to lay your hands on Nokia's most powerful phablet and the lack of several LTE bands is not a dealbreaker for you, be sure to check the retailer's website at the source.
source: ExpansysUSA via WMPoweruser