That’s because it is not an error…it is damage. Some kind of counter mark. …imo…Spark BTW…Welcome to Coin Talk! Go to error-ref.com to discover what real errors are and how they happen. Also, go to doubleddie.com and read everything. It will make you a better collector.
Definitely damaged as that’s a counter stamp. Not sure by whom or for what but it’s basically damaged. Not a mint error of any kind. Welcome to CT.
Keep this always in mind.. Just because something looks different, weird or strange on a coin doesn't automatically make it a Mint error. There are plenty of ways coins become altered and/or damaged after leaving the US Mint facility. You Quarter has a added counterstamp of the numbers 9 11 It looks to be a reference to the September 11th, 2001 attack on the World Trade Center in NYC. I unfortunately had to endure that crazy mess since we live about a mile from ground zero. Welcome to Cointalk
