Cleaning a medieval coin restoring its silver coating

This tiny french coin (15mm) had long remained undefined. Looked like a roman or celtic bronze coin. We first start by removing the crust with the glass fiber tip of the precision pencil. A cross appears, meaning it’s no antique coin but medieval. Such coins were usually ‘billon’ coins: a copper heart with a silver coating. Unfortunately the silver coating has disappeared. let’s restore it ! We use our needle to clean the remaining solid crusts. We nned to get rid of the patina so that the coin goes back « raw ». We use the brass brush of the precision pencil. All patina, meaning here an annoying oxydation, is withdrawn. The copper heart of the coin is now visible with its pink color. We decide to apply our famous Silverfinger on the coin. We let the coin try to absorb the silver liquid for 10 minutes. We get rid of the remaining liquid. Then let it dry. The coin is now cleaned, with its long lost silver coating restored. It’s a François 1er Double Tournois dating 16th century. The last picture shows 2 similar coins. The one on the left was just cleaned, its oxydation has not been removed but unfortunately the silver coating is gone. On hte right, it’s our coin we purposedly removed the oxydation to be able to apply a new silver coating.