LOL Don... *chuckles. Happiness is very important. Poor pat got all frightened ;-)
In any case, yes I meant ground mounted. My bad for neglecting to point that out. I thought that as I did not say M16, you would know I meant ground mounted. But how can you read my thoughts to know what I mean when others are less stickler-ish and I too, often get sloppy?
But yes, there were 4 (IIRC) Quad Fifties at Dien Bien Phu. Martin Windrow they were M45C Maxson skeleton type, with M18 reflex AA sight, mounted on a M20 one-ton two wheel trailer, the combination designated M55. Windrow claims that they were prepared for indirect fire at the south of the airstrip. However, at Epervier; the location I am familiar with them from, they were used to mow down a Viet Minh Mass assault on the Bailey Bridge together with 4 105 mm Howizers firing directly at the enemy over sights at point blank range. There is a picture of one of them
here and on a Hanoi Museum
here.