It is also possible, even probable, that this musket was in a state inventory and was not converted for that reason. Many states were severely lagging in their militia arms maintenance programs, conversions were not progressing rapidly anywhere until the emergency of 1861. Many state regiments, both North and South, went into service carrying flint muskets, even fighting their first battles with flint arms. Stonewall Jackson was still requisitioning flints for his troops' muskets as late as the Valley Campaign of 1862 and beyond.
Another indicator of state as opposed to Federal service is the name carved into the stock, something that could happen in pre-War state service where discipline was almost always lacking unlike Federal service where defacing equipment was a severely punishable offense to say the least.