The original LeFaucheux patent was a single locking lug that when rotated 90 degrees allowed the barrel(s) to move forward and down. In comparison to the Jones Underlever that has two camming surfaces that pull straight down and when properly fitted have not just the hinge pin but also the radius shoulders and the camming surfaces acting as bearing area. The Jones is the strongest of the break action designs, it just happens to be slower than later designs to open/close.

HTH

Colin