The Reenactment Group that portrayed the 23rd had the butt plates and thumb escutcheons of a bunch of their Pedersoli muskets engraved, I have been informed, several decades ago. As they have passed or left the hobby, these have begun to appear on the market.
Unfortunately, the engraving of a person's name on the butt plate is not a historic manner of marking the musket, unless the musket was a private piece belonging to an officer. An Enlisted man's name would never have been engraved on property that belongs to The King.
The thumb escutcheon was a normal location to mark the company and rack number for a King's Musket either LLP, SLP [such as the Pedersoli] or IP type. However, the engraving used for this run of the 23rd muskets was in a modern font. An officer's musket would not have had a rack number.
Several have popped up on Gunbroker and other sites , often priced as much as a brand new Pedersoli Bess, but with the engraving which (imho) doesn't add to their value.
There's no reason though that the muskets would be anything less than a good functioning gun and a good shooter.
LD