English watchmaking in 1800 was a craft system of extraordinary depth: Lancashire supplied movement parts, London finishers assembled and regulated, and the trade's reputation rested on the fusee, the detached lever and the chronometer.
That same system resisted mechanisation. The fusee persisted long after Continental makers had adopted the going barrel, and the division of labour that had been a strength became an obstacle: no single firm controlled enough of the process to redesign it around machines.
Swiss établissage was similarly distributed, but it was organised around interchangeable ébauches and specialist finishing, which adapted more readily to mechanised production. American factories went further still, designing movements for machines from the outset.
By the 1880s the English trade was competing on price against watches that were both cheaper and more consistent. Coventry's attempt at factory production came late and never reached American scale.
For collectors the consequence is practical: an English watch of 1870 and an American watch of 1900 belong to different industrial worlds, and should be researched using entirely different sources — hallmark tables and retailer records for the first, factory serial records for the second.