Mike,
It sounds like you got an answer. The only tricky part is the fact that it is a "proto". The knife is somewhat of an anomaly. It is still a Buck knife, sorta. The hope is that it would be worth more as a prototype but a possible problem would be that Cumberland is not that well known. Another problem is that, at least with the Buck collectors i have talked to, if it is not an official Buck project, they are not too interested in it. An example would be the Yellowhorse knives. This was a collaboration between Buck and Dave Yellowhorse and therefore, the knives are very collectable. I get many calls from members about to buy a knife asking me if Buck made it or was it done "aftermarket".
On the other hand, I would have to think that it is worth at least what the going rate is for a standard one and I could not fault a guy for asking for a premium since it is a proto. You never know.
Hope this helps!
Joe
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Joe Houser
Director of Quality, Buck Knives Inc.
Buck Collectors club Administrator