That airframe sits on a pad in front of the US Army Aviation Engineering facility (Aviation Applied Technology Directorate - AATD) in Ft. Eustis, Virginia (37.166921 N,-76.60188 W on Google Earth!) It was built and flown by Bell Xworx engineering, and by US Army test pilots, and set an unofficial speed record back then. The wings and thrust offset the rotor, which was loafing along for the ride at high speed. Its final high speed was 275 knots in level flight, about 15 knots faster that EC/Airbus (really?) X3 and 20 knots faster than Sikorsky X2, and 60 knots faster than the Lynx official FAI record that still stands.
The highest speed trial was flown by Lou Hartwig, Bell Experimental pilot and Duane Simon, chief Army test pilot and great guy. Duane told me that at 250+ knots, the 2 per rev vertical vibration was eye-watering, but worth it. The whole story is posted in the bottom comments on:
Bell 533 helicopter - development history, photos, technical data
Duane Simon described an emergency landing here:
http://articles.dailypress.com/1994-...pter-work-aatd
Making the 533 three-bladed would use a gymbol head, where the teetering rotor would still be used, with a hub ring that attaches the blades, and that teeters to keep the mast happy. That teetering head would have been similar to the V-22 rotor head, which is teetering, also, for the same reason - keep control moments low and keep mast/transmission light weight.