[Boatanchors] Mounting system for old aircraft meters?

[Charles]

I have in my junk box a working GE 0-150v, 400 Hz aircraft panel meter, 
p/n 8AW61LVA200, basically identical to this one: 
https://www.ebay.com/itm/234333775889

Scrolling to the bottom of that ebay listing, there are other similar 
instruments that all appear to use the same mounting, whatever that is. 
Mine says Convair spec FZC-4-1368 and is stamped Next Inspection Date 7 
62. Googling isn't coming up with anything except ebay as I mentioned.

Does anyone know how these are mounted in panels? The face end has fine 
threads around the outside, 2" in diameter and appear to be 32 tpi if I 
measured correctly. Could there be a bezel with a square face that bolts 
to the instrument panel and an internal 2"-32 thread, and these meters 
screw into the bezel?

thanks for any help. I know little about airplane dashboards ;)