Ron Guth: Under the Edict of October 1738, all of the earlier French coins of 30 Deniers were recalled and replaced with a new billon coin with a value of 24 Deniers. Additionally, a new Sol valued at 12 Deniers was struck from 1738-1748. The following mints produced this coinage: Paris, Rouen, Caen, Lyon, Poitiers, Limoges, Bayonne, Toulouse, Montpellier, Riom, Dijon, Perpignan, Reims, Nantes, Troyes, Lille, Amiens, Bourges, Rennes, Aix, Metz, Strasbourg, and Besançon.
Although billon is already an alloy with a low percentage of silver, many of the later issues were debased even further. In extreme cases, the only silver in the coins was a thin plating applied over the surfaces. Thus, it is not uncommon to find circulated examples with a copper color. Conversely, examples with a high percentage of the original silvering still remaining are sometimes quite rare or non-existent.