I have the following descriptions:
"The Sikorsky S56 was a heavy transport helicopter used by the USMC. Four prototypes were ordered as XHR2S-1 with serials 133732/133735 and the first flight was on 18 December 1953.
This was followed by 55 HR2S-1s with serials 138418/138424, 140314/140325, 141603/141617, 145855/145875 whilst production of 138425/138431, 141618/141645, 143828/143863 and 147101/147136 was cancelled. The first flight was on 25 October 1955 and those aircraft remaining in service on 18 September 1962 were redesignated as CH-37C.
The designation HR2S-1W was allocated to an early warning version of which two examples were built with serials 141646/141647. They carried a large radar radome."
"Intended to be a heavy assault helicopter for the USMC three XHRH-1s were ordered on 15 March 1951 with serials 133736/133738 but were eventually cancelled in 1953. A full scale mock up was built and they were to be fitted with rotor tip jets."
Gyrodyne designed, but not built, a similar looking helicopter. I don't know the designation or the timeframe, but a picture is attached.