This photo and article featuring a Ford GP was published June 09, 1941, in the Democrat and Chronicle out of Rochester, New York. It highlighted Major Harry Miller’s jeep modification, which added a 37MM gun to the rear of the vehicle.
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Originally posted February 07, 2015: This post emphasized the Camp Lewis connection.
This June 9, 1941, article from the Spokane Daily Chronicle notes the Ford GP belongs to a Fort Lewis unit visiting California for maneuvers.