Balisong age?

[prober996]

I remember giving this knife to my father many years ago (1980s?) and now it has come back to me after he passed. The blade is marked Balisong U.S.A on one side and has the butterfly logo on the other side. I think that that nylon sheath is original as well, although I am not 100% certain of that. Based on the markings and photos, can anyone help me to determine its age? Thanks in advance.

[prober996]

Going through my father's papers, I found the original pamphlet (attached) that came with this knife when I bought it for him in the late 1970s or early 1980s. It turns out this Bali-Song USA knife is quite valuable (the same model knife sold for $1475 on Arizona Custom Knives). The knife is the Wee Hawk model, and was ground by master knifemaker Jody Samson. There is a picture of him at the grinding wheel, in the upper left corner of the top image.