Current configuration, double bungee visors, HA-LP/PPB oxygen mask.
Except for the supplemental boom mike bracket, the initial configuration of the HGU-55 during its introduction in the mid-end of the 1980's represented standard issue.
The HGU-55 replaced the Gueneau 316. There was not a real evaluation, the HGU-55 deemed the best option regarding system compatibility with the just introduced Northrop F-5E Tiger II.
The other possible competitor was the Swiss proto Titlis, that in terms of comfort and weight worse than the helmet it was supposed to replace.
The installation of double visors and related oversize visor stops took place at a later stage.