What is the value of a 1975 Winchester model 94 30-30 serial number 3356619 with a round 20 inch barrel in excellent condition?

Check some of the on-line gun auctions and gun shops and compare prices. (keeping in mind that the asking price isn't what the gun actually sold for) Kittery trading post has reasonable prices, Cabella's is a little high. Both have large enough selections where you should be able to find something comparable. Gun shops are only going to offer you 50% of what they think they can sell it for, so you could take it to them, see what they offer, and then double the price, but private sales are normally lower then retail so don't get too excited. Winchesters are hot right now but this isn't an unusual model.