There were some Kowas that long time bird watching people, the ones who know their optics, would practically fall down on their knees in front of, they were made for use in the shooting sports at some Olympic games or other in the 1980s. I have a later top of the line Kowa scope from circa 1990 that I have yet to see matched, but I don't claim to be an expert on them or their value. What I suggest is to search out bird watching sites online to try to find a going value, I don't buy much second hand stuff so I can't be entirely helpful there either, but the site that I'm aware of is birdforum.net. They have a very good optics subforum, a place to start anyway, and you could in fact ask about the value there and get an honest answer- optics geeks abound there and they'll jump on bad information.