Vet Of WWII, Korea, Vietnam

[WateringHole]

While I was in my doctors waiting room yesterday, there was a elderly man in a wheel chair wearing a baseball cap that had "WWII, Korea & Vietnam Veteran". I asked him if he was a vet of all three and he said "yes". I asked what outfit he was in Vietnam, and he sounded like he said "mc vee" in 66/67. He said it was an artillery outfit. I wanted to ask him again to repeat his outfit, but that's when his name was called and the man that was with him told me he's a retired Master Sergeant before he wheeled him away.
I was wondering if any of you Vietnam Vets ever heard of such an outfit or one similar to that pronouncitation.