Hi Spiral,
I saw some similar to these at an auction....I thought they were unusual blades...because of the three 'fixing holes'. Luckily a 'farmer type' informed me they were 'cutters' from a farm machine.
I saw 3 'ethnic spearheads' on eBay, recently, with the same rivet hole pattern...but not with curved blades (long tapering triangle)....but these had remnants of green paint
I could be totally wrong about these....but the wear marks around the rivet holes suggests great force elongated the holes and ripped the rivets out....
Regards David