What causes this to happen on the edge? It goes around the whole edge. Maybe some type of planchet flaw? Thanks in advance.
remember a planchet is feed into 3 dies .. the Obverse - Anvil, Reverse - Hammer and the Collar is the surrounding. When the dies are smashed together it pushes out the planchet (which is slightly small) edges and the Collar forms the correct size. So if there was something on the edge of a properly formed coin, then it would be something on the collar .. or some damage after it left the mint. In this case 17 years of potential timeframe for something, someone, somehow to roll the edge on something. Without seeing the entire coin ... whos knows. And even if we did see the entire coin front and back (which may have other potential indicators of how it may have been damaged), we'd just be guessing. For instance when coins get stuck in laundry mat dryers (when they fall out of pockets and thru the always broken lint screen) they start causing various damage even around the entire edge (as one example)
I believe @Fred Weinberg or @JCro57 addressed this issue, but I can't locate it right now. Hopefully, they, or someone else can answer this question again.
