THE SWISS HGU-2
Apart from a reference in the 1974 Pilotenzuteilunglist, which defines it as an alternate of the H-5 on Mirage IIIS - to our knowledge there are no official documents about a possible evaluation/ commissioning of the HGU-2 in the Flugwaffe.
Nevertheless, we have in our collection specimen of Swiss AF HGU-2s and we are aware of photographs of said helmets taken on different occasions, which in some cases may help in tracing their supposed origins. Attempting to put them in chronological order:
A first one is identifiable in the hands of Ernst Saxer, during the 1965-1966 Swiss AF live firing trials of the HM-55S (AIM-26B) Falcon air-to-air missile that took place at Holloman AFB.
Possibly supplied by the USAF for his F-100 chase plane back seater/ photo flights; later kept and then used at home leaving part of the USAF ADC reflective tape in place.
Its comm equipment consists of H-143/AIC receivers, MX-2088/U ear pads secured to the helmet shell via nylon strings as in the early HGU-2/P versions.
The second one is a heavily modified "Gentexite" HGU-2A/P. The shell features the three ventilation crown holes and is fitted with a British Mk.2 visor, as with the H-5s in service at the time. The helmet has installed an H-5 comm harness and spring loaded H-154/AIC headset; a "banana mount" (MT-522A/U) enable the installation of a (French ELNO or M6A/UR) boom mike.
Although in its current configuration it is supposed to have been used mostly on helicopters and prop aircrafts, oxygen cast receivers are present, and as mentioned above, the HGU-2 would appear to have been considered an alternate to the H-5 on jet. We are aware of other similar specimens in other collections.
The third and most recent one appears in some pictures taken at Meiringen AFB in 1979; sporting a "Tiger" single visor cover decoration, fitted with custom leather edgeroll and MBU-5 oxygen mask.
In this case it could be assumed that the HGU-2 were provided to CH F-5 pilots during the aircraft evaluation or while attending the air combat training which took place at the USAF 425th Tactical Fighter Training Squadron, Williams AFB, Arizona.
The below still from a Swiss TV broadcast filmed in 1982 shows the DH-151BAMF-1 helmet of a Swiss (? see below) F-5E pilot sporting an Alcombury (GB) USAF 527th "aggressor" squadron sticker.
A recently published book confirms the (hush-hush) presence of US agressor pilots in Switzerland in the early 1980s. Therefore the participation of Swiss pilots (even more hush-hush, see neutrality...) engaged in training session at Alconbury cannot be ruled out.