Each knife is handmade by Bruce Bohrmann and considered quite valuable. You can try to contact him, send him a photo, and see if he can date it for you.
That was the impression I got...the ad was from a July edition of that paper. His son has a knife sharpening business in the same area and has a facebook page. He may be able to assist you as well.
My name is Andrew Bohrmann and the knife you have was made by my father Bruce Bohrmann. His email address is bbohr@maine.rr.com. My father will be able to give you specifics on this knife.