The image is upside down.
This shows one I had with back bracing arm partly bent back. I added the little white dots on the picture to show the fold-over edges.
Main body width is 21.7 cm
Width including the attaching tabs (2 on each side) 23.9 cm
Height 24 cm
Made out of one pieces of sheet metal.
Here is an original PASS plate. This shows the other side with the UNIT SIGN. This particular one was repainted on this side only in the 1970s by a previous owner. I got this from Dr. William Gregg, but he had not painted it.
COLIN