More reading show the 51/p is F-111 specific 

Flight helmet is a HGU-51/p… mask was (?) modified for use with it… it’s close    no doubt you have a one off..👍👍

https://www.salimbeti.com/aviation/helmets7.htm

I found this on Salimbeti’s web site

Drive up north a bit to Orange County and visit Vintage Productions

Thanks Kurt.  I didnt lean that way mainly because it lacked a Tbar pin I see on a lot of late 19th century items. 

Agree with Kurt

Simply amazing!   -Ski

Take it to private messenger. Soliciting on the open forum is prohibited.

So I’m in a bit of a pickle, I spent hours searching for this radio transmitter harness to know when it was issued and where it was used in. I know for certain it had to be during Vietnam due to having Nylon Straps but I was left with nothing.  I’ve looked at dozens of photos and looked at all models of these harness and not one of them showed this exact model and it’s been driving me crazy. I am hoping of you guys have the answers to knowing when it was used and which radio it housed in. It’s such an odd ball harness with little to no info