Great job Jack!
Your photography is very sharp and the nomenclature you have used for the various parts and aspects, while not always the same that parker Bros. used, perfectly describes function.
The only change I would suggest is that "K" is the mark of
Charles Alonzo King, Superintendant of the Gun Works and inventor of some few dozen improvements to the Parker Shotgun. C.A. King's son Walter King succeded him as Superintendant and used the stamp "WK".