Although it -looks- like a copper plating bubble and 'rust burst', the square 'hole' in the center of the disruption is too 'square' to be a CPB, imo Looks like damage to me,
Looks like a hole made from a square head screwdriver used for wood screws. But zinc rot has set in and will just get worse.
T03 - you're probably right - someone saw the copper plating bubble, and decided to puncture it....and then environment took over