On Aug. 13, 1954, the Delta-wing Gerfault became the first plane in Europe to exceed Mach 1 in level light on the power of a turbojet alone — without rocket or afterburner.

These covers were arranged by the late James Wotherspoon who maintained correspondence with the European test pilots. The pilots mailed them when they had a chance.

The ramjet-powered Griffon was a further development of the Gerfault design.