Re-chipping and re-basing are a huge problem in the artifact collecting hobby. 50-75 years ago there was very little value in "Arrowheads" so old time collectors would pretty em up. Look for extreme patina change and look for added notches. A jewelers loupe is a must and a UV light will pick up re-chipping on many materials.
Examples of altered pieces. Note patina changes:
Examples of altered pieces. Note patina changes:
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