It is just a die chip. No added value although some like to collect them. Also not considered a mint error just normal die wear etc. that causes chips.
Not from the mint that's for sure. This is what will eventually happen to all Zincolns after a few years out in the wild, weather, ground etc. Might have started out at the mint with some plating issues. Time and enviro factors finished it off. Still costs more to mint these zincs than what they are worth. The end may be near.