I live in Jackson County MO and I found one very similar to yours. I found it on a creek bank with three small points after a heavy rain. That portion of the creek wall had collapsed exposing them. They were all covered in a dark grease. I always assumed it was from a decayed deer pouch. The one that is similar measures 2 1/8 inches long by 1 1/8 wide. The three small "dart" points measure 1.5 inches for the two longer ones and 1 inch on the shorter. The notched object is thinned in the middle. Haven't figured out what mine is either.
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