I can’t tell much from your pictures, they are to dark. Try some better lighting and also post a full obverse and reverse picture.
I thought split plating to but I read that only occurs on copper plated cents starting 1982 to present
The irregular shape on the bottom curve of the bust may have been caused by a chipped die. Would like to see full photos also.
On zinc pennies. This is a quarter though. This quarter has an outer copper color to it. Seems it may have been plated and that area for some reason didn't get the plating on it.