I believe that you have a 1768 revision of the 1766 Charleville that has had the frizzen replaced some time in its long history. This was common for muskets to be repaired in the field. Also it was normal for them to be repaired after the war. The feather spring on your musket and the pan look to be authentic Charleville. If you look closely above the name "Charleville" you might find a faint "D" with a star above it. I see nothing that would negate believing it to be an authentic Charleville of the model that was given to the US by the French and that was repaired long ago. The aging of the frizzen and the frizzen screw suggest to me that the repair was done in the 1700s.
If you could show a close up photo of the inside of the lock, it would help.
Here is some information on the Charleville Musket history:
"The Charleville musket served throughout countless conflicts including the American Revolution, the French Revolution, the Napoleonic Wars, and the War of 1812. It was manufactured in the French Royal arsenal in Charleville, France (Champagne-Ardenne region). It was the standard issue flintlock musket of the French Empire throughout the 18th and the early 19th centuries. The original French musket was delivered in 1717 and was continually improved through the years until an all-new model was issued beginning in 1763 near the end of the seven years war (French and Indian War to us). The 1763 production form was reinforced for the rigors of combat but these additions proved in excess and the added weight to an already unwieldy and long weapon. The Model 1763's sturdier design proved to be a bit too heavy, so in 1766 the musket's design was lightened. The barrel wall was thinned, the lock was shortened, the stock was slimmed, and the Model 1763's long iron ramrod cover was replaced by a pinned spring under the breech. The trumpet shaped ramrod of the Model 1763 was also abandoned in favor of a ramrod with a lighter button shaped end."
"Though usually considered to be a separate model, the Model 1766 was often referred to as a "light Model 1763" musket, especially in U.S. Revolutionary War invoices. Despite being thinned down, the Model 1766 proved to be rugged and reliable. The Model 1768, is in fact a revised version of the basic 1766 musket. The primary differences are a third spring loaded barrel band and the movement of the bayonet stud to the top of the barrel. The musket is 59 inches overall as opposed to 1766 model that is 60 inches in length."