Those are called Bullmoose bars and designed by Tom Ritchey. Very popular in the EARLY days of mountain biking. More info and replacement (sometimes, expensively) available here:

http://www.rivbike.com/products/list...product=16-198

I had a bike or two with those. Like all early MTB-specific parts, they weighed a ton but were quite literally bomb-proof. Well, depends on the bomb - they probably wouldn't survive a large h-bomb but would probably stand up to a small tactical nuke.....