Do you know that he was ever in the military?
What you have attached is a draft registration card, and all men of a certain age were required to register. Not all men who registered for the draft were ever drafted or enlisted in the military. Your John was age 47 at that time, so likely too old to have actually served.
Information about this draft registration from the National Archives:
On April 27, 1942, the Selective Service conducted the fourth of six draft registrations. This
registration, also called the “Old Man’s Registration,” collected information on the industrial
capacity and skills of men born between April 27, 1877, and February 16, 1897 (ages 45 to 64).
This draft registration was not intended to be used for military service, but to provide a complete
inventory of manpower resources in the United States that could be used for national service.
