The Nubia X is an Android smartphone with a 6.26" 1080x2280 IPS LCD display on the front and a secondary 5.1" 720x1520 AMOLED display on the back. The X is powered by a Snapdragon 845 chipset and features 6/8 GB of RAM, 64/128/256 GB of storage, a Dual camera - without a Selfie camera as the OLED can be used for that.
The Nubia X is now shipping. You can find it on eBay starting at around $699.
5.1" 720x1520 AMOLED