Virtually all militia muskets were the personal property of the individual militiaman so it's not at all surprising that some should be "personalized." This isn't at all uncommon. I have two with extensive silver wire inlay as well as silver escutcheons. Also, if the inlays aren't there, how do you know they were sterling? Could they have been tutinag (a British form of nickel silver) or brass? In any case, silver ornamentation on ordinary militia muskets isn't at all unusual.
In the purely British context, the subject does become confusing when we get to Volunteer muskets made for members of units recruited from the well-to-do. Outfits like the "Inns of Court Volunteers" where all of the privates came from the same social and economic station as officers were sometimes equipped with muskets that are effectively indistinguishable from officer's arms. That said, the fuzee was going out of fashion by the late 1790s – it was really a product of war in North America and although it almost certainly saw some use in Europe, it never seems to have been as much. In an American context, there is a question in my mind if they were ever commonplace as late as this gun, which is clearly post-War of 1812 and probably dates from about 1816-1820. Certainly it is well known that Washington would not allow their use in the Continental Army. Some militia officers may have carried a musket but given the lack of social distinction between officers and private soldiers in the American militia they may not have been much difference between those and any regular private's musket. Very little militia saw any active service after the War of 1812 and the officers' sword was a far more significant reflection of social status and authority.
When I see "officer's fuzee" I generally think of an arm specifically made for an officer – not any musket an officer happened to carry. Again, in the British/American context these were never an item of issue.
