The proven microprint reader. 
The idea is very simple. 
Copiers and printing techniques are getting better and better. So banknotes can be printed better. So good that to the uninitiated they are deceptively similar. 
So we need something that sees better than meets the eye. 
Correct: the magnifying glass. 
But the magnifying glass can only magnify 5X. So even stronger. 
The microscope. 
Correct. But microscope is big, needs power and is expensive. So what now? The answer is 
– Magnifies 20.4X 
– Costs less than 10 € 
– is the size of a credit card.