I was at a gun show last weekend (yes, we still have gun shows in Commiefornia) and saw a top cover with Northridge. It looked like a 1919 but the top nut had a screw in it rather than a pin with cotter pin assembly to hold the lever in place. It was right next to some M37 top covers which had the big blocky lockup in the rear but the ones I'm refering to had what looked like a regular 1919 surface for the rear lock face. Was this screw assembly a later product improvement over the pin/cotter system that sometimes fails when the pin breaks or works out (had this happen twice to me). Anybody know?