Sometimes a goldsmith's maker's marks evolve over time and knowing what mark was used when helps the jewelry historian or appraiser accurately dating an item.
In France, historically, the Administration de la Garantie stored copper plates on which maker's marks were stamped (by law) creating a record of the mark. At some point these were all destroyed, leaving us without this valuable historical reference.
The Antique Jewelry University has an extensive Maker's Mark Database to which new marks are added every week. You can help build this database by sending in images and information to firstname.lastname@example.org or by posting 'm in our . If you would like to help on a regular basis you can use the same email address to request an account.