I have verified the over 200 knots from more than one source.  Not sure about the 300 knots though, only this source mentioned it.

YUH-1B:  Used as an aerodynamic test bed as the "Model 533" and modified to a number of configurations as part of a US Army program. The first series of modifications, flown in 1962, features aerodynamic fairings, a new tail surface to offload the tail rotor, and a tilting rotor mast inside a large fairing structure. The Model 533 was then fitted with a swept wing, two Continental J69-T-29 turbojets, and a modified rotor blade with swept tips. This compound rotorcraft achieved a speed record of 236 mph in level flight on 15 October 1964, and on 6 April 1965 topped that record with a speed of 250 mph in level flight. It was finally fitted with two wingtip-mounted Pratt & Whitney JT12A-3 turbojets. In this configuration, it achieved speeds of over 300 mph.

Looks like one of those kids toys "Transformers"