Microsoft publishes a list of specific Lumia 950 and 950 XL variants receiving new firmware
Earlier today, we reported that Lumia 950 and 950 XL would be receiving firmware updates in select markets. Microsoft has now published a list so that we know what those markets are.
Before anyone gets their hopes up, the AT&T model of the Lumia 950 is still not on the list.

To view the Manufacturer Name (Device Variant) and your Mobile Operator, go to Settings -> Extras -> Advanced Info on your device.
Firmware updates were also made available today for the AT&T model of the Nokia Lumia 830 as well as the LG Lancet and the Microsoft Lumia 735, both of which are Verizon devices.
Source: Microsoft via Windows Central