Aurora made all the Universal Monster molds in the 60s, including the Hunchback/Bellringer. They went corporate in the 70s and folded, leaving all those molds out there. Revell and Monogram both used the molds at different times in different capacity, glow in the dark, Luminators, etc, but I don't think they ever did the bellringer.
Polar Lights (a play on Aurora Borealis) bought up the molds and in some cases had new molds based on the original masters (Bellringer, Bride Of Frankenstein, Munsters Living Room) and released them.
In short, a lot of those kits floating around can be under 4-5 different company names, but the Hunchback is either Aurora or Polar Lights. If it was in a box, even with the Aurora logo, chances are it's Polar Lights, unless you paid a couple hundred for it.