I think this is a great idea. Also, take the Dime for example. Many with over 1 or 2 billion. Try imagining a Dime with a serial number of 1,234,567,890. Better yet I would think the numbering would be sequential from all years so there could not be a duplication. So now with that as a thought, imagine a Dime with the serial number of 1,234,567,890,098,765,432,111 stamped right accross the face.