During World War I, the U.S. Army developed mobile operating units mounted on trucks to provide surgical care closer to the front lines. These units could be set up in under an hour and were designed to treat severely wounded soldiers, especially those with abdominal or chest injuries who could not be safely transported long distances.

Description: Dark military brown body, dark military brown chassis; brown seats; dark military brown 12 spoke wheels; gold plated parts; red cross in white circle on front of roof, sides and rear doors; 'US' on lower sides of vehicle and '31' on upper window panel and rear door in white lettering.

Variations: No known variations.

Notes: This model is packaged in a maroon J-type window box.