58-5524 served as the prototype H-43A. It was a former US Marine Corps HOK-1, BuNo 129839, which had an accident at Camp Pendleton on 19 September 1956 and was rebuilt by Kaman with the new four-fin tail. Registered as N298B it was first seen in April 1958. By June 1958 it was marked as 58-5524. The 18 production H-43As had lower serial numbers. 58-5524 was used for various tests at Bloomfield until it was retired in early 1963. Information from Johan Ragay's H-43 website. Photo from: Nederlands Instituut voor Militaire Historie