It has 960 x 540 display resolution, which is supported by Windows Phone 8.1 update 1. The size specs of 139.97 x 71 hint about it having a 5-inch display. So, it very well looks like a mid-ranger slotted between Lumia 630 and Lumia 730.
RM-1090 is the Dual-Sim variant, while RM-1089 and RM-1091 are Single-Sim variants. RM-1091 is the latest to pass certification at FCC. Surprisingly both Single-sim variants come without LTE as seen in the FCC certifications and unlike Lumia 635 / Lumia 735
So, this device looks set for a global release. Also, the announcement mentions “a Microsoft Lumia device” and in terms of leaks, we have only seen RM-1089 / RM-1090 /RM-1091 revealing themselves. So it doesn’t take a genius to figure out we and Microsoft are talking about the same device.