A new Lumia with RM-1090 / RM-1091 product code was first revealed from Adduplex database. The device seems China / Asia bound and has a 960 x 540 display resolution, which is supported by Windows Phone update1. Now, this device has visited FCC and the certification reveals that RM-1090 is the dual-sim variant of this device and seems it will be Dual-Sim Dual-Standby device like other dual-sim Lumias.
Outside of USA, the transmitter of the device is capable of operating also in GSM/GPRS/EGPRS900 and GSM/GPRS/EGPRS1800, HSUPA/WCDMA900 (Band 8) and HSUPA/WCDMA2100 (Band 1) which are not part of this filing. This is a dual-SIM device. As both SIMs use the same antenna and transmitter chain, full evaluation of this device has been made by activating a single SIM only.
The size specs of 139.97 x 71 hint about it having a 5-inch display. So, may be it is a mid-ranger slotted between Lumia 630 and Lumia 730, specifically targeted to China (Asia) market with bigger display and slightly higher resolution than Lumia 630 and its variants. It uses battery BL-L4A, which is not used in any other Lumia device before.