That was posted already, and it's 1.5 DIN. That's an industry standard designation.
But... (saving you the time to look at the thread): 7" x 3" (Standard DIN is 7" x 2" / Double DIN is 7" x 4")
The mounting holes are centered (1.5" from top/bottom) and are 2.5" back from the front.
The front-top 3/8" is beveled, so they would likely want to put the holes 2.0125" back. (or maybe just 2")
That should give them all they need to know.
I haven't checked, but it should be close to the size of a Whelen Cencom control panel (only deeper).
EDIT: CenCom is 6.875" W x 3.5" H, so the 200 is 1/8" more wide and 1/2" less tall, but darn close. The overall plate would take the same rack space.