IT'S WORTH THE INVESTMENT IF YOU TRAVEL
I will get googly-eyes for this one but I will take the stare down. If you travel as much as we do and exchange a tremendous amount of money in foreign countries you never know what type of US currency (legal/counterfeit) you will get in return upon a purchase. In most countries you will spot a three-legged dog before you see US currency so when you get it you should be concerned if it is legit or counterfeit.
The most common places to receive fake bills are taxis and night clubs or bars. It is unlikely that an ATM, hotel, restaurant or store front of any kind will pass on counterfeit bills. Anyhow be prepared especially with taxis because in any country they are the first to take you for a ride. Now, there are ways getting around being scammed by using a simple $4.00 investment on a $5 to $100 return. It is called a counterfeit pen.
So, how does a counterfeit pen really work and how can it tell if a bill is fake or not? It is pretty simple; real bills are printed on cotton fiber paper and do not contain the starches (contained in regular white printer paper) that react with iodine. Therefore, when a bill is genuine, the pen will leave a colorless or brownish mark; if however the bill is counterfeit and printed on regular paper, the pen will detect the starch and its mark will turn black.
The next question is, can counterfeit pens work on foreign money? The answer is yes, if it is a Universal (US & Foreign Currency) Counterfeit Detector Pen. Counterfeit money was a relatively common scam in many countries in years past, but as newer, larger denomination bills arrive made with better technology the amount of fakes reported are decreasing. But hey, be like the banks, they don't trust any currency so you should be of the same mindset.