I believe it was only Unique, It was a neat little gun, friend had one , had a chance to shoot it. It sure wasn't a target pistol or rifle but accurate enough to give the Starlings hell.
As Jim Watson posted It could only be set up, one or the other, a small pistol or a carbine , not as a stocked pistol. Too bad no pictures, that is probably what it is but who knows . Rare? I don't think so, scarce , maybe, for a number of reasons, the main one is that it didn't sale that well.