It was 5 bucks at a flea market, the woman was selling modern household items and no other artifacts or antiques, and said her husband just found it a few days before in a Peoria Co field. She seemed completely innocent and honest and didn't know anything about "arrowheads" so there was no suspicion of deceit, plus it has some tiny fresh fleabites showing a much more "white" chert versus the more patinated beige surface so seemed legit to my untrained eye. I know that patina and polish can be faked by more sophisticated forgers but sincerely doubt that she would have gone through all that trouble to fake a damaged point to sell for 5 bucks. It still has the dirt on it as-purchased, and it appears as though the left 75% in the first pic was the rain-washed exposed portion when picked up.
I have no idea what the notching should or shouldn't look like but it seemed OK to me.

Thanks for your thoughts!