I just found an article about Robert U. Milhoan in the February, 1966 issue of The American Rifleman. He was educated as a mechanical engineer and worked as a civil engineer on the design and construction of railroad and other projects. He started his education as a tool and die apprentice.

He never apprenticed as a gunsmith, he worked for the Three-Barrel Gun Co. in Moundsville, WVA, and for A.W. Peterson in Denver.