11/15/2006. Remarks by David Hatcher
: "This may be the first civil variant of the UH-1B. Note the luggage compartment door on the tail boom, dual pitot tubes, different cabin door window and lack of hard points. The four blade rotor system became common on Bell helicopter from August 1979, when the Model 412 was first flown, however in the sixties three and four-bladed rotor systems had already been test-flown, including on the Model 533 compound helicopter."