My Congrats to Rob for perfect answers!
There is a book about the Bell HSL-1 by an aeronautical engineer, pilot and aviation writer Tommy H. Thomason: "The Forgotten Bell HSL: U.S. Navy's First All-Weather Anti-Submarine Warfare Helicopter."
The Bell HSL is the ancestor of every ASW helicopter to follow. Bell's first and only helicopter using tandem rotors until that time (first flight in 1953), power was one 2,400 Hp P&W R-2800-50 mounted just aft of the back two wheels of four wheels widely spaced fore and aft, with the control cockpit forward of the front wheels. Each rotor was two-bladed with balance weights at 90 degree angles to the rotors. Each rotor mount was near the extreme ends of the fuselage. It was intended to use air-to-surface missiles such as the Fairchild PETREL and dipping ASDIC.
Rotor diameter was 51'6" each, gross weight 26,500 lbs, range 350 miles at 100 mph.
Three prototype XHLS-1s were ordered and delivered; the first flying on 4 March 1953. Fifty production were built as HSL-1s beginning in January 1957 out of a contract for 78 total, with 18 intended for Britain's Fleet Air Arm. I don't think those 18 were ever delivered, but Rob just might know. U.S. Naval service was short-lived.
Technically, the HSS-1 Sikorsky SEABAT later operated as EITHER a sub hunter with dipping ASDIC or as a sub killer using launched torpedoes, but not both simultaneously from one platform. Paired HSS-1 sub hunters and sub killers were possible, but the usual was to call in a Navy Destroyer craft to do the killing when a target was located by the hunter.
I haven't checked here, but any photo of the Bell HSL is welcomed.