The F-Type was most likely a development derived from the era (early 1950s) British leather and cloth helmets. The rugged gray-colored open-woven used in its construction was a step up from the natural materials in use at the time and their problems.
Characterized by the new style of earphones of less thickness and more comfort, fitted with elastic chin and nape straps, the F-Type was the first British-built cloth helmet provided with a "UK NATO" Type 671 communications connector installed.
The most visible difference with its successor, the G-Type, was the number of helmet side “pull the dot” fittings (three) instead of the latter's five.
On the F-Type, the oxygen mask (usually an H-Type or A-13A/1) was secured with a strap suspension harness/ hook system as in the past;
The G-Type instead was designed for triangular metal plates provided with three pull the dot fittings to be attached to either side of the helmet, the mask donned and doffed by means of a metallic wire toggle assembly.
Both F- and G-Type could be worn under an Mk.1 (A) protective helmet shell.
The F-Type has at least two connections with Swiss AF: test pilot H. Häfliger wears it under a modified Mk.1 helmet shell with American (P-?) or Swedish (FFV-?) inspired protective visor during test flights of the ill-fated P-16 fighter-bomber;
And in a photo most likely taken in Dübendorf in which one supposes, even if the Mk.1/1A never entered service with SAF, the evaluation of its possible replacement with a prototype “Sportex” product.