T-Bone,
I was JTF team member twice-Laos in 98 and VN in 02 and I worked on pilot fight equipment in the USAF. Your dad's story hit home in a very personal way for me.
If he gets it back have him send it to me and I'll restore it for him (if he wants)
That is quite a job to have. My hat is off to you. I'd bet the happy endings are few and far between.
Right now my folks are mapping out a vacation trip to the area. The village where the helmet is located is very remote. He'd sure like to get his hands on it and visit his aircraft crash site.