(AP Photo/Jon Elswick, File) Counterfeit bills can look so real that they pass the pen test and even some banks are having trouble spotting the fake ones. Phony $100 bills are turning up in Florida, but good counterfeit money is rare these days. Over the last few decades, the U.S. Mint has greatly increased the security of the currency you see out there. The bills passed in Florida have been based on the older ones made before the new security measures took place. The key to the money is actually the paper it’s printed on: Real currency is made of fabric and cotton, not a wood-based product. The pen is designed to find regular paper, and while we’ve all seen the pen, the Secret Service said the best way to find counterfeit money is to compare it to another bill, but with every transaction seeming to happen at high speed, cashiers rarely have time to examine the money. The most popular bill being counterfeited is the $100 bill overseas, but here in the U.S., it’s the $20 bill, and the holiday season is when the most counterfeit bills start floating around. How big of a problem is this in Southwest Florida? The Secret Service said in our area, they recover about $5,000 to $6,000 a week, and while that sounds like a lot, the agent said it’s a very small amount compared to other parts of the country. Also, the last person holding the note is the one who loses the money, so check it carefully. RESOURCES Secret Service: Know Your Money (pdf) Secret Service: How to Detect Counterfeit Money The U.S. Currency Education Program Dept. of Treasury: If You Suspect a Counterfeit