I would sooner think the abnormality on you coin is a blister of sorts as the mintmark is no longer hand punched onto coin dies.
It's a single zinc bubble, as opposed to a plurality of them. They are pretty common as zinc is absolutely not meant to create long-living coinage.
The proper term is "Plating Blisters". This is from error-ref.com: The 2017 D Lincoln cent has a plating blister after the word WE.
Wrong. Last chance 2012 liberty what wrong with it and reguardless or not how do I unsubscribe to coin talk