The US Army got a limited number of four-seat (O)H-23F Ravens, equivalent to the civilian UH-12E-4, apparently from 1962. There were four with fiscal year 1959 serials, 17 with 1961 serials, of which 61-3218 was changed to an OH-23G, and six with 1962 serials. Powered by a 305-hp engine they were intended for hot and high environments according to Hiller. The OH-23G went back to three seats. Hiller seems to have ignored the quirky tail number system in which the decade digit of the serial should be left out. Photo from: Hiller