Wow, that's clean. 1984 sounds about right and if you could find someone who is looking for vintage Stumpjumpers this one would be worth a pretty penny. If you don't have an interest in it and just want to sell it, I'd put it up on fleabay with a buy-it-now price of $500 or best offer. You might find someone willing to pay that or if not you can find out what the market will bear.

That's a very solid bike in fantastic condition but most of the value is in the nostalgia of the thing.