That is a great document Scott.
The late 1813 to early 1818 was a very convoluted period for musket production for and by the Federal Government. It is considered to be a transitional period relative to muskets from the Charleville Pattern 44-1/2" long barrel to the U.S. Model 1816 Flintlock Musket. For example, Springfield Armory produced eight different distinct pattern muskets with 42" long barrels in this period based on stock configuration, barrel band configuration, lock configuration, and markings.
These 1815 Contract Muskets were reflective of the quickly changing musket configurations having early Type One 1812 Standard locks, 42" long barrels, cheek recesses, but Type Three barrel bands with the retaining springs forward of the lower and mid bands.
Incidentally, arms researcher and author Peter Schmidt was the first to correctly identify these 1815 Contract muskets in his book
U.S. Military Flintlock Muskets Vol. I , published in 2007.
Below is a photo of an 1812 Standard Pattern musket produced at Springfield during the period these 1815 Contract Muskets were being made.