The story goes that once upon a time coins were evaluated by the amount of precious metal contained in each like these ancient Greek silver coins.

These are made of electrum which is a naturally occurring alloy of gold and silver. Not only are they of irregular shape, the edges are smooth with no marks or scratches on them.  So, for example, a $10 coin contained the precise amount of gold or silver that was equal to $10 in gold or silver by weight.  Cheaters used to cut the edges off coins to melt them down and make new coins for their own profit. Preventive measures had to be taken. This was quite a serious issue since not every man could carry a pair of scales to check whether the coin was cut or had its proper weight.

To tackle the cheaters tricks, it was decided to gouge small lines on the coin edges. Due to this they became distinguishable enough to tell if the coin was tampered with.  This extraordinary method was suggested by the very famous at that time and nowadays, physicist and Warden and Master of the British Royal Mint, Isaac Newton. The idea seemed to be simple and brilliant at the same time. Eventually, all coins were marked and swindles dropped to zero. And no wonder – when one came across coin with smooth edges, they knew at once it had been cut or tampered with and would not accept it.  Now you know the rest of the story.