The RWR display is an IP-1310/ALR azimuth indicator. It's the size of a standard 3.25" square face instrument as per MS33556.
Draw a square 3.25" on a side. Round the corners with a 0.125 inch radius. Place 0.170" diameter mounting holes in the corners such that they are 0.125" in from the corner edges. The instrument glass is centered.