They are pretty rare. I've never saw one. I might be to the point that if I see one, I'm going to buy it, just because. They were also in 45 colt.
The High Standard Sentinel Mark II and III were made by Dan Wesson. The Crusader was an in-house design, and as far as I know, made by HS.
IIRC Dan Wesson somehow had an influence on the Crusader as well. Whether they designed it, or Dan Wesson produced it as a HS design, or it was a HS version of a DW, something to that effect. I bet they're a good quality gun.