This tread has started well but is becoming less and less interesting,
so I looked online:
History
a bit more information there about the gazelle heritage (development of the platform: Alouette II and III)
the published reference agrees on 264Km/h (140Knots) cruise and 310Km/h (170Knots) VNE
There is somewhere on YouTube a Gazelle doing 160Knots as I remember.
I think the interesting point is that both the gazelle and the Hugues500 are speed/ maneuverability leaders. Design wise it was obtain in different ways:
1_ the gazelle on one side, low parasite drag + fenestron + loads of power.
2_ The hugues500, a 5 blade rotor that enables less rotor diameter (faster NR), thus delaying advancing compressibility, retreating stall.
Am I on the right track?