Jack,
Serial numbers were discontinued at HF in 1812 per Moller Vol 2 page 72.
I am not an expert in any way relative to HF longarms. In my opinion, there are no real experts on antique arms, just knowledgeable amateurs.
Your musket looks to have been cleaned pretty aggressively at some point particularly if the View, Proof, and serial number are not present on the barrel. That is the case with the many of these old flint muskets. Harpers Ferry flint muskets have not survived in the numbers that Springfield flint muskets have so it is a nice musket to have.
If you live anywhere near Virginia, take it to Cliff Sophia at CSArms gunshop in Upperville. Cliff is extremely knowledgeable on HF arms.
Kent