How old is this detector

From Fisher history...

Demand for the metal detector spurs growth

In 1936 Fisher Labs moved to a small building at 745 Emerson St. in Palo Alto to meet the growing demand for the Metallascope, which was nicknamed the M-Scope. Shortly thereafter, Dr. Fisher was granted a patent for his invention. The M-Scope became the accepted standard for all types of electronic metal detection. Geologists used it to locate ore, treasure hunters found treasure, utility companies pinpointed buried pipes, lumber mills detected metal inclusions in sawn logs and law enforcement uncovered abandoned and hidden weapons. In 1939, just prior to World War II, Fisher moved to an even larger building in Palo Alto at 1961 University Ave. During World War II and the Korean Conflict, Fisher Research Labs was called upon to contribute its technical competence to the war effort, but the M-Scope business was never neglected.

So it goes back pretty far, this one I am not sure but early.

Build style looks like the early 1940's to me. The original patent model was nicknamed "Mscope" in about 1936. Possibly it's the 10th revision?? Mscope model 10 - M10?

I hope it is ok to post this link. If not, delete with my apology. - Link