This looks like it might be a Pro-tec Classic Full Cut helmet that has had the ear cover cut off. Lots of the "High Speed, Low Drag" guys wear these in boarding operations on ships and the like, when you are more worried about slamming your head against a low hatchway than a fragmentation grenade.
USCG Boarding Officer teams, USCG Drug-Interdiction, SEALS/UDT, SFOD-D, EOD, etc... sometimes wear helmets like these, but they were more prevalent from the late 80's through early 2000's. Alot of these teams started upgrading to the current generation MICH/ACH/Lightweight Helmet that now are MUCH lighter than the PASGT helmet and have a neutral buoyancy.
I cant testify to them being used as a liner for other helmets, but I believe the guys that know way more than I do about it (Cobrahistorian and Hawkdriver)
Here is a pic of the "Pro-Tec classic Full Cut helmet" with the ear covers intact
Also remember that alot of Airsofters saw Blackhawk Down and wanted "To be just like Delta'' and bought these and modified the ones they found in Skate stores. Alot of the ones you find are in this ilk.
Edited by Misanthropic_Gods, 24 October 2009 - 09:56 PM.