If you are interested, here's the manual:
AV7600VOR
There are two on eBay at the moment. One has a "Buy It Now" price of $65.00 (but the battery will not hold a charge) and another has a "Buy It Now" price of $130 but he doesn't know if it works or even what it does! That's eBay for you!
Basically, it is worth whatever you can get for it. If there is an airport nearby that has a flight school, you may want to contact them and ask if one of the instructors knows if one of their students is looking for a "starter" radio or if you can post a picture and description on their bulletin board.
OR...
Put it on your local Craig's List. As long as it works, $100 sounds fair to me... but of course I am not in the market for one at the moment.