This is an old metal on/off switch by MEM, which is stamped with the name STARTET
It is very heavy (over 2 kilos) and the rectangular box part is 5 and 1/2 inches x 4 inches and 3 and 1/2 inches deep
Imprinted on the back is CA 239
3M
In reasonable condition for it's age with scratches on front and back and some rust. It also has one corner with a small piece broken off, which I have tried to highlight in my pictures.
I think it would clean up nicely