On the 2 side opening Pboxes on Lancaster LRs shown in RCA 1, the button is in the Bplate heel disguised as a screw. I've used this location on a few LRs and used a separate button made from an unthreaded portion of a flat head screw w/ the slot filed off. The push rod is made from a length of approx. 1/8" nail. Using a separate button allows the hole to be centered in the heel and the screw "head" is inside the heel and contacts the rod. The catch riveted to the the lid and the latch spring mounted to the bottom of the recess are of standard design.....Fred