"Pre-Ban" won't really have any bearing on it's value ... the thing that will make it valuable is that dancing pony on the side.

If you have an account on Gunbroker, you can do a search there for similar guns that have sold (don't judge prices based on asking price, judge them by what they're actually going for. You'll have to log in to look at "completed auctions" listings, but a GB account is free).