Hi Pnutar et al, It appears that all production HGU-53/P helmets were made to the same 1988 contract but the configuration was updated through the production run. I have seen one manufactured in 1993 as well.
The main visual difference between the HGU-53/P versions is the visor operating mechanism. I have noted three different as seen in the attached picture. The first is a limited procurement helmet for operational test and evaluation, the second is an early production helmet (like the November 1991-dated one in the eBay auction) and the last a late production helmet (an August 1993 dated example was sold by 'navyfastjet' on eBay some time ago). The last version appears to be the most commonly found configuration.
Cheers, Bluelight
