I have owned three similar muskets. I know that, although designed by France and issued to their own troops, as this one seems to be, the armories of Liege, Belgium made many, many knock offs of these arms. Except for the Liege markings they were identical to those of St. Etienne. I don't know how many of the 'made in France' models wound up here in the US but thousands of those Belgian knockoffs did and it is possible that because the Liege copies were so common all of these arms, whether from France or Belgium were called Belgian rather than French so it may be difficult to separate them. One thing. The OP refers to the arm as an 1842 T. It is my understanding that the T was added to models originally made in flint and converted (or Transformed, hence the T) into percussion. As I look at the arm it looks to me that it was manufactured as a percussion lock to begin with, not converted from flint. It is, by the way, a beautiful arm and all were well manufactured. I assume by the sights it is a rifled gun. Do you know the caliber?