I haven't been able to get any help on this. I've researched to find similar look from other coin having the same capped die striking error. But the rounded edges with no ridges have local coin dealer in town clueless.
simple.. Heat or Acid damage Wait.. rounded edge.. It's heat damage then. Your Quarter was trapped between the wall and the drum of a clothes dryer. It is called a Dryer Coin.
If it weighs less, the dimensions are different from a normal coin and the surface is granular is probably acid shrunk
Wheels, the weight of the coin is 5.45grams. But after comparing in size they're the same in width. But tcoin is bigger in circufermence than the normal quarter.
We will never know what exactly happened to your coin but I don’t believe is any type of error. Normal weight is about 5.7-8 , yours has endured some shrinking which is what happens when they are exposed to acid
With a micrometer my coin is slightly bigger in circufermence than the unmutated. The thickness mics out to be almost identical as well.