Another thing this instrument could be used for is measuring the case depth of an polished, etched, harden specimen to verify the case depth is correct. I see the words "scratch microscope" Can't make out all of the verbiage and I don't know what this meaning is referring to other than measuring a scratch? Maybe someone with higher knowledge than me can tune in and comment. I also noted the date if 1956, one year before I was born. That's an 61 year old instrument. I'm sure it's been obsoleted and replaced with something much more modern.
A good reference is to go over to "Instrum's" website and do some searching for a similar instrument.
Ken