This is a case for the Banana Pi R3 Mini board.
It has 3 antenna holes for the small stubby antennas that often ship with the board and 4 that can be used for 4 MIMO 5G/LTE antennas.
It also has holes on one side of the case to provide ventilation for a small 5v fan. I used a Noctua NF-A4x20 5V.
It can be mounted using the 4 holes for m3 threaded inserts.
Likewise, the frame has 8 holes (4 on top and 4 on bottom) that provide threaded insert mounts.
The author marked this model as their own original creation.