Quote Originally Posted by KWK1 View Post
Knibbs' book says they added the fillets to aid latch alignment when the hinge wears and becomes wiggly. The catches don't allow for movement on the side and front buttons.

I seriously doubt the duck bills left the factory without consistency of the angle. Forged parts are consistent. The dies don't allow for that much variance. They get bent from abuse. The end is bent way over on my LJ "H the Lincoln" second batch. And one of my "BSA AIR RIFLE" standard rifle arms is bent down.
Maybe they were dual purpose as on p42 of J Knibbs book the illustration is described as "cocking lever catch with strengthening fillets".