I see, a very poorly researched (understood) auctioneer's description with the information possibly taken from the owner's inaccurate story about his/her gun. The comb on this example appears no different than it did when manufactured in France for the French military's use.
It is also interesting that the auctioneer says "Unlike French locks, this specimen lacks an internal bridle on the tumbler." They photographs do not show this feature of course but why would the French have manufactured this lock without the internal bridle?
The next two sentences are - "This item lacks any markings and were likely 'cleaned off'. During the American Revolution the lock making was restricted to Pennsylvania." Okay, those are confusing so let's just ignore them as fluff. I will say that the markings could have been, as he said, 'cleaned off', but not during the Revolution, the vast majority of arms imported from France were in good condition for immediate issue and use and there was no reason for removing their markings. The markings on the locks were not deeply stamped and often, post-war refurbishment removed them partially or wholly. The refurbishment and repair for the New Republic was usually done at the at the Schuylkill Arsenal near Philadelphia, the first Federal arms facility. The Schuylkill Arsenal was the successor to the early Philadelphia workshops where arms and military supplies were repaired, made and distributed during the Revolution.
The last sentence "This firearm is a well used American Charleville musket which was assembled at the Continental Arms Manufactory in Philadelphia." With that he completely negates his earlier statement "These muskets were altered in France specifically for the use of American Revolutionary war soldiers." Why or should I say how, would the French alter a musket that hadn't been made yet?
I think you can ignore the statements in the auction brochure.