I received a US100 bill recently with EAR stamped on the back. What does that mean and can you still use it?

I received a US100 bill recently with EAR stamped on the back. What does that mean and can you still use it?
If it actually is a legitimate piece of US currency, the stamp on it will make no difference. If you wish to confirm this, bring it to a bank and have them authenticate it and/or you can ask for a replacement bill.