Along with the other competitors evaluated in the mid-50s, there was the P-3.
First assessments revealed an essential flaw. It was shown that the P-3 was not compatible with the Martin Baker ejection seat configuration.
During tests performed with a borrowed Martin Baker ejection seat training rig it was found out that the upper ejection seat initiating handle got entangled with the helmet's visor yoke protruding handle.
An additional drawback was the fact that the visor obstructed the field of vision of the pilot, even if the former was fixed in the raised position.
Fitted to the helmet is an A-13 A oxygen mask.
More about the on the Swiss AF 1950 evaluation page.