Re: Iver Johnson .22 single shot derringer
15,000 made in pretty much the time period you stated. These are one of those guns that although not common are also not really rare. Add that to the fact that there aren't a large number of collectors that are interested in them the value usually is nowhere near what you were finding as pre-auction values. Usually these little pocket pistols only bring decent money if they are in excellent condition.
I think the dealer that offered you $60.00 was about right as a wholesale value. I would estimate the "retail" value at around $100-125 if the gun presents a decent appearance. (Sounds like the trigger spring needs replacing. Not a big deal.)