Margo, a banjo with four strings and a longer neck than tenor, depending on the actual length, is likely what's called a plectrum banjo. I point this out just as additional background knowledge for you to have when you speak with potential buyers. And you might want to assure that your Craig's list entry includes that description.

Tenor banjos are designed and almost universally used as chordal rhythm instruments in jazz and rag, although of course many excellent players can push the envelope and get more lyrical music out of them.

The idea and practice behind plectrum banjos is less oriented toward rhythm backup and more toward single-note lyrical use.

Those observations, again, don't go very much toward your question about value, but give you background, and may help you in finding your sales market.

Dave Oesterreich