Today they have virtually no purpose other than to allow the blind to tell a quarter from a dollar and perhaps a dime from a cent. But the purpose was originally to keep people from shaving silver or gold from the edge of the coin and passing it on in circulation.
Right on! According to the PCGS Grading Guide, the screw press was developed in the late 15th century by Donato Bramante. Getting the edges machined took longer. The invention of the Castaing device in 1685 was the best of a long line of attempts. A hundred years later, it was employed at the US Mint though even into the early 1800s, half dollars were still struck "open collar." It might be that we all spend too much time inspecting coins with a magnifier without understanding how they were made. This is perhaps less true of world and ancient collectors. The same might be said of paper money and its aficiandos. I share the same guilt. I had to look up the Castaing machine and I still do not know if this is how DECUS ET TUTAMEN first was inscribed on the edges of British coins or who the monarch was. There is so much to know.
