Thanks for your answer but I’m pretty sure it’s not environmental. The brown areas are copper colored and looks like a cladding error.
Sorry but it's staining from environmental exposure. Here is what a real partial clad looks like https://www.error-ref.com/partial-clad-layer-before-strike/ Notice how your stain is diffusing into the unstained area while coin in the link has an abrupt change from copper to clad
This is not Silver. It's a clad coin. Environmental Toning like @potty dollar 1878 said. Very unusual but anything can happen in numismatics. Good Luck!
That quarter was laying with other items covering parts of it as it was exposed to something that changed the unprotected areas. Just ED, environmental damage, NAV, no added value, so worth a quarter.
Not an error, just toning. Something was on to and under the coin in the not toned areas. If it was missing the clad layer the copper would look totally different. Sorry I don’t have a photo but missing a clad layer is unmistakable. Welcome to CT.
You can recreate that. Lay a few overlapping coins in a small amount of soda and let the soda evaporate. Pull them apart and wash off the sticky goo and you will have a half moon toned coin…… It happens every day in automobile cup holders all over the country….. Welcome to CT.
Before that was a coin or even a planchet it was a blank that was struck from a long plated strip. When those strips aren't entirely plated the ends are copper resulting in the copper on the blanks and later on the coins. The shape of that discolored area is the giveaway that isn't the copper core.
I'm pretty sure it is environmental exposure toning. Here is an example from a metal detecting find.. I found these laying on top of each other. Each quarter covered just a part of the next protecting it from exposure. Same thing happened to your quarter somehow. Worth? 25 cents
