That Is One Expensive Pin!

it was probably done when the coin was in circulation and probably by someone that could afford to use such a coin for decoration and not miss it. They had to be of wealth to do so but I have seen many gold coins done this way so it must have been a popular thing back then with the wealthy

Edit: after looking at it again I noticed this is in a bezel not soldiered to the coin itself so the coin probably isn't damaged unless the bezel has marked up the coin. The older ones I have seen had the clasps soldiered straight onto the coin itself

Occasionally, I come across coins that have holes drilled in them to make bracelets, as well as some that have been soldered a tiny bit on their edges. The former are hopeless, but the latter are somewhat salvageable.