You may possibly be getting a little short-changed at $7,000. I'd do a lot of research before you accept an offer.
FWIW, there are a couple listed on eBay right now, one at just under $42K, and the another at over $12K. One sold at auction for over $76K just two months ago. Could be yours might not be in as nice of shape, or might not be as rare a variety as some of these... I don't pretend to know, I just did a couple minutes' worth of research.
Everything is "worth" what someone is willing to pay, be it a lot or a little. I'm just saying I wouldn't jump all over the first offer without being really sure it's a fair offer. If it's genuine and it grades high enough, you might consider hitting the prospective buyer at double his offer and then meeting in the middle.
Just like if you are looking to buy a big-ticket negotiable-type item (car, etc), you're probably not going to take the first price offer. Same thing applies when you are selling and your buyer is the first one to throw out a number. "$7,000? I was thinking more like $13,000". Then let the games begin.
For a small commission, I'd broker it for you.