In a few weeks is my grand's sons birthday. I want to send him a birthday card with a brand new $100 bill inside. My concern is does the PO scan the mail looking for money being sent? Is that blue metallic strip on the $100 bill detectable? I don't want to send the card and money and then have the DEA, FBI and Postal Inspectors arrive at the door with my birthday card in hand. Am I over thinking this too much? I don't want to send a check because I think he will get bigger kick of getting a $100 bill.