I would not be surprised if the coin itself was struck on another coin- Bingo- Charlton says- "Beginning in 1692 and continuing through 1698, a new issue of sols marques was made. The design was new, but instead of being struck on fresh blanks, many were struck over previous issues of sols. It is sometimes possible to detect parts of the undertypes on the overstruck coins.The new issue was rated at 15 deniers when it came out."
Also, "In 1640 the French Government called in all douzains and counterstamped them with a small fleur-de-lis in an oval to change their rating to 15 deniers. The term sol marque (marked sol) came from the fact that these coins were counterstamped. It later came to apply to all sols. "