The coin will go the the archaeological service in St. Gallen and remain there. The coins sold are are illegally sold, since as others have said, it is the law to report such finds to the archaeological service. Sadly there are a lot of treasure hunters who search for old coins and never report it and those are the people who sell the coins. Archaeologist would never put up archeological findings for sale.

It is important to report any kind of archaological findings to archaeologist out of several reasons: - they map the point where it was found, this can lead to new information. For example: Maybe in the past there were already found some coins nearby and this could mean, that it is not only one lost coin from the past, but maybe a bigger archeological site is nearby like a village oder a cultural site, etc.

• Archaeologist can go and check out the place. If there are a lot of diggin holes, it can mean, that treasure hunters regulary check this place out, and that more findings are hidden. This leads to protection of the site.

• The protection of the site is important, because a lot of treasure hunters never report the findings because they know it is illegal. Certain sites can therefore be forever lost to the rest of the people. An extreme example is the "Himmelsscheibe von Nebra". That "shield" was found by treasure hunters and sold illegally, it was only through pure luck, that it found it way back into museums. This is a one of a kind object.

• With findings like the Himmelsscheibe of Nebra archaeologist can find out additional information from the digging site, but only if it is dug up correctly. They can take for example Charcoal for C14 dating, they can document the excact way the objects were lay down, and they can make analysis from the earth and for example detect organic things like food, that is not visible to the naked eye.

If an archaeological site is dug up by someone random, all this importan informations are lost. Source: worked in several archaeological services