Steve, this has been asked a couple of times before, but never answered except that these were produced from 1990 to 1993 at the time when a few other relatively unusual Third Gens were coming off the line. I've seen references to three departments that used them, but other than that, you'd probably need to get it lettered from Roy Jinks to find out actual numbers.
By the way, over the production period these came with all three of the different styles of trigger guards, according to the SCSW.