This is a Notable Operational milestone.
The aircraft (XE521) was piloted by W. R. Gellatly and J.G.P. Morton.
The Rotodyne still holds a world speed record (in the E-2 Rotodyne sub-class).
See AHS Calendar November 2014 for more details.
A history of the design and development of the Rotodyne is provided in the Wikipedia entry.