The New Money

So what's the "bell in the inkwell"?

You handle cash every day and that makes you the first and best line of defense against counterfeiters. Every person or business that receives a counterfeit note experiences a real economic loss. If you accept a counterfeit note, it cannot be exchanged for a genuine note, and it is illegal to knowingly pass a counterfeit note.  

Check out www.newmoney.gov  to learn about the security features of the banknotes you are handling.  The bell in the inkwell is a new security measure embedded in the new $100 bill.  Learn more about additional security features in this interactive reference.
http://www.newmoney.gov/newmoney/flash/interactivebill/10_InteractiveNote.html