This will be going to geocachingireland.com's 3rd Annual Irish Caching Event in Donegal next fortnight. It really is a small world. I/we can only imagine what it must have been like in Vietnam. We'll try and get your coin to Europe.
About Donegal and it's relevance to the coin - during WWII USAAF aircraft were allowed to overfly County Donegal (in the Free State, later the Irish Republic) to bases in County Fermanagh (Northern Ireland). Many of these aircraft were manufactured in the United States, to be flown by the RAF. This was known as the 'Donegal Corridor'.
Navigational markings are still, faintly, visible on mountains in Donegal. There were many unfortunate crashes into these mountains. The bodies of dead airmen were handed over at the border. At the border the Guard of Honour performed a drill with reversed arms, a Bugler sounded the Last Post and a Chaplain gave a Blessing.
An Allied officer, embarrassed that the coffins' journeys were being continued in open lorries, thanked the Irish for the "honour". The reply was: "Ours is the honour, but yours is the glory". (some of the above from wikipedia, on "Irish Neutrality" http://en.wikipedia.org/wiki/Irish_neutrality)