So, there's the Indian Springs 140 up there. There was also a bigger version that looked just like it, but a little longer. IS 180 or 210, I forget which.
Then there's this. It's a factory hopper, not some cut/hack job. No idea what it is, or how many there were, or how many are left floating around out there. I bought the gun it was with at a pawn shop essentially to get this hopper.