Need Info: Just Picked Up a Fisher 600t

I just found one of these today at a garage sale for $10. It works, but I know nothing about it and couldnt find anything on the web about it.

Can anybody here tell me a little more about it, or maybe point me to something on the web? Are these valuable at all? I was going to give it to a friend.

I snapped a pic http://www.krakboi.com/forsale/fisher%20600t.jpg