Your friend has some beautiful looking pieces. In that top frame, 2nd one down looks like one I have , but yours is a much nicer looking piece of flint. I always thought it was broken or unfinished. Now it appears to me it is an intentional single corner notch. (excuse me if my terms are incorrect.)
see pic..
Much earlier stuff, IMO, than what you're finding on your farm. The one-shoulder knife probably isn't a Scottsbluff Knife (looks like one at first), although the transverse flaking on the blade is right for one (unless they also made them by burin-flaking like yours). Mostly Plano/Early Archaic, I'd guess, and very high quality EA at that.
Burin flaking is what you see on the base of the Cody Knife : a removal at a right angle (or close to it) to the plane of the blade edges. Ordinarily, burin flaking produced burins -- little tiny chisel edges for scoring & engraving. The bases of Decatur points are burin flaked. It was one of the Early Archaic technological carryovers from the Paleo era that pretty much disappeared afterward.