Former Marine here, I saw this thread the other day and began thinking who was the best to contact. CID, O&I or Naval Intelligence. Finally I decided the best thing might be to contact the unit Commander of 1st Recon.
You are right, recon is a specialty unit in the Marine Corps made of special teams.
It's been years since my connected service so I'm not sure of the movement of the various unit designations. One thing to keep in mind is just because he was assigned to 1st Recon doesn't mean he ended his service in 1st recon.
One thing does strike me though is 1st Recon is a west coast installation. I'd assume but can't be sure he entered service from somewhere on the west coast. I'd think he would have entered boot camp in San Diego and got advanced infantry training in Camp Pendleton. Then moving into his field of Recon, also in Pendleton.
So if you entered the Marine Corp on the east coast, You would go to Parris Island, SC for boot camp, Camp Lejeune for Advanced infantry training and Lejeune for recon school.
Having said all that and since ya'll have some letters prepared I'm giving you an address to the 1st Recon Battallion Commanding Officer. Of course more than one of you may write.
Lieutenant Colonel Brian L. Gilman
Commanding Officer
1st Reconnaissance Battalion
PO BOX 555300
Camp Pendleton,
CA 92055-5300
Thanks for looking out for our Marines