This is an alternate cover for the "GPS-cover 64" (if one does not use MKGPS).
The dimensions correspond to the MKGPS board, as to all the other MikroKopter boards like the Flight-Ctrl etc (holes spacing: 45 x 45mm).
Alternatively, this board can be used to mount any other element, like your receiver etc. in the following picture for instance, it is used to mount a universal GPS antenna (you see here under the down side of the board):
Scope of delivery