There was a McDonald Plymale born in Braxton County, West Virginia, July 13, 1903. Could this be the Max you are looking for?
He is listed in the 1910 Census as Max, living at home with his parents William Calvin Plymale and mother Eliza.
There is also a WWI draft registration for a Mack Mc Donald Plymale living in Randolph County. He is listed as a teamster working for the Wilson Lumber Company (the year 1918). It lists his birth as July 13, 1900.