Copper is softer than nickel. While your coin was in an acidic environment, the acid ate away the copper core. Can you post photos of the other two sides of your coin? I believe we'll be able to see some acid damage to the cupronickel outer clad layers.
here are the two sides of the unsealed quarter, looks normal, not sure, I have had it put up for a long time. thanks for your input.
It does not look normal You can see the letters and numerals close to the rim. There is also a mushiness to it all. This is evidence of acid damage. I/we have seen this plenty of times.
I remember someone once told me that ppl did this tied a thin string like dental floss and dropped it in soda vending machines then pulled the quarter back out. How true it is IDK but it seems like it wouldve worked.
