Herself has an elderly aunt who owns a c.1966 Martin 00-C-18 that she can no longer play. She was once a music teacher and is now living on Social Security. The guitar is in good condition, with no significant scratches or dings. Jenn wants to give her a fair price for it, as much to get some cash into her hands as anything else. I've looked on e-bay and the Elderly Instruments web site so I have some clues on what the "retail" price would be, but please give me some ideas on what you'd expect to get if you had such an instrument and sold it.