I have no idea whether it's rare or not, but I've heard of only one other besides mine--surely there are others. It's a Kit Carson Small Model 4 with Stellite 6K blade and carbon fiber handles. The unusual feature is that it has no liners or bolsters--just the carbon fiber slabs and backspacer, and a sliver of hand-sawed, hand-mortised titanium for a lock bar. The result is a 3" blade, 7" overall knife that weighs 2.2 oz. -- a full ounce lighter than Kit's standard Small Model 4.
Maybe this is just a special variation on a well-known theme, and not what you're looking for.
I will say, though, that this has been my EDC since late October of last year, and I can't imagine a replacement that would equal it for high cutting performance and low-maintenance durability, in a package that utterly disappears from my consciousness while in the pocket.
-w