There is no possible way to figure it out, unless you know how it was damage or if you damage it. There could literally be a 1000 different explanation how it happened. Whatever it is, it happened after it left the mint.
Agree ,damaged after it left the mint. It could be a collector found it and realized the ground/worn part on the left lower rim was damaged and made the sharp lines to be sure no one thought it was a mint error, that is what I do, they still spend. Jim