That's very interesting, Dave!
I know nothing about this Henry Moll/Mull.
Breidenhart seems to have arrived in Lancaster in 1752 or 1753 and by 1757 owned property on Queen Street--which, a decade later (after it passed through other owners), Dickert purchased. In that 2013 article, I speculated that either he or Roesser trained Dickert.
Breidenhart is not listed in the 1765 Lancaster city tax list as a gunsmith (I think he's listed as a tavern keeper): the only men listed as gunsmiths are Dickert, William Foulks, Roesser, and John Henry (William Henry's younger brother).
Breidenhart is, however, one of the gunsmiths hauled before the Lancaster County committee of inspection in November 1775 and was forced, with other gunsmiths (Christian Jack, Peter Reigert, Michael Wither, Jacob Kraft, Peter Gonter, John Miller, John Frederick Fainot, John Graeff, Peter Reasor), to make muskets instead of rifles. Presumably Dickert was not hauled before the committee because he was already in compliance with its demands.