The Flues single-barrel trap went thru three different boltings in its brief barely eight years of production, while the Knick was produced for at least 60 years.
Parker Bros. went through all kinds of changes -- T-Latches, lifters actions with back-action locks, lifter-ations with front-action locks, top-action hammer guns, hammerless guns without rebounding locks, hammerless guns with rebounding locks, then the 1905-style bolt-plate to take up wear, then the 1910-style bolt plate to take up wear, then they simplified the action a bit and went to a coil top-lever spring in place of the older V-spring, etc., etc.
Lefevers were in a constant state of change -- side-cockers, cocking rods, thumb-roller top latch, side-swing top-lever, conventional top-lever, two-hooks, small hooks, large hooks, sears on the sideplates, sears hung in the frame, on and on.
