What make / model(s) of wrist-worn altimeter was the military using during the Vietnam War?

If I ever needed one, it would have had to display negative altitude half the time, as I layed in rice paddy water.

Chief, generally speaking, wrist mounted altimeters weren't used then. The altimeter was mounted with a stopwatch on a board over the belly mounted T-10 reserve. You can catch a glimpse of it here:
https://www.youtube.com/watch?v=uCqPFLl1T-g

I don't recall the make and model but the ones we had were off the shelf commercial models. I did find my goggles in a box of junk a few years ago. They were leather WWII vintage aviator goggles.