It capitalized on readers' familiarity with American Machinist, McGraw-Hill's popular trade journal.
But the usage could have benefited from some branding discipline, because of some little confusion over whether the title was properly "American Machinist's Handbook" or "American Machinists' Handbook".
It is doubtful that Industrial Press's Machinery's Handbook (1914) was a mere me-too conceived afterwards in response.
The eager market for such reference works had probably been obvious for at least a decade before either work was compiled, perhaps the appearance of the McGraw-Hill title merely prodded Industrial Press to finally get moving on a handbook of its own.
American Machinists' Handbook, co-edited by Fred H. Colvin and Frank A. Stanley, went through eight editions between 1908 and 1945.