I bought a Quest/Bentley housing for a TR101 about 4 years ago. Don't have it anymore. Should be the same housing you're looking at. Mine needed some work so I found the original lens and switch suppliers both of whom still sell parts.
I also have a bad xerox copy of a manual for the housing. It says that the housing is:
Depth rated to 350'. Individual housing tested to 150' for safe scuba.
Not sure what the difference is but I've had mine to 80+ fsw.
One problem mine had was that the fitting on the front of the housing had a hairline crack in it. The original seller didn't notice it, nor did I until I tested it. There's a really thin o-ring embedded in the mating surface of the lens/port but this crack occured in the threaded fitting that the knurled ring screws onto. I think it happened because someone overtightened it. I was able to make mine work anyway with a little custom engineering (filed it flat) and another o-ring that mated to the flat part under the ring. Something to check before you buy it.
The other thing to know is that the port is only good to about 50% zoom, beyond that it loses focus fast. Wide angle works fine.
Quest did go out of business around 2001. Sometimes housings/parts of housings show up on eBay.
I liked the housing, it worked and never leaked during a week of diving. One quirk mine had was that when you plugged in the LANC cable, the jack had to be oriented vertically down or sometimes the controls wouldn't work. I got used to starting the camera on the surface to check this. Also with that big flat thick backplate, I'd think they're more susceptible to leaking if smacked during entry so I always had it handed down. The o-ring is grooved into the plex, but it mates to a 3/8" wide flat poly surface. Not the best design I've ever seen.
hth, PM if you need the parts supplier info or copies of the manuals.
