Howdy
The Janus is a RARE gun and price is hard to set for that model. I got mine for $1200 and it was very used but complete. I would have paid 1500 for my gun or any Janus at the time. The price would best be set by an auction, but I would venture a guess of between $1500 - 2200 depending on condition. IT would be an easy sell. And yes the Janus was a different version of the Scoremaster. Some if not all were put together by the Master-gunsmith of Detonics at the time, Richard Niemer. Mine has papers with instructions for care and feeding along with a brief history of the Janus gun. Hope this helps!
L8r
Conley