I suggest you look here for some previous sale prices:
https://cdnpapermoney.com/notes/register/7/3/18/74/320/list$3000 seems like a fair assessment based on actual sales, though you might have to settle for slightly less. If you can get close to that figure privately, then I would take it and run. Otherwise, just auction it in one of the major auctions. This particular note is a bit oversold and in this condition it's not exciting enough to attract much action. It's nevertheless well-established so you'll find a value-buyer for it.
I'll have to respectfully disagree with Dean and say that you absolutely
should get it graded if you want to maximize your sale price (especially at auction). I know that some old-timer collectors have a bone to pick with the grading services but the fact is that if it's not professionally graded, your buyer is guaranteed to nit-pick over every minor defect and hold you personally accountable. Would you rather sell it as a raw EF to appease the Charlton Standards hardliners or as a professionally certified AU-55?