Are you referring to the caduceus marking which is flanked by the "US" device? If so, this was introduced post-WW2, likely in 1947 when the Army and Navy Medical Departments were merged.
Ben MajorMRC Administratorben@med-dept.com
1943 Harley-Davidson WLA
1943 Douglas C-47
1944 Cushman 53 Airborne Motor Scooter