Hello everyone,

I have a question about early 1900's pin tumbler Sargent keys. I have a cylinder from I'm guessing 1950's or earlier that has five pin keys but six pins in the lock. It appears that the 6th pin is the deepest cut possible; keys are clearly cut for 5 pins with a notch in the tip for the 6th pin. It looks just like old Russwin cylinders that had the "guard pin" in the 6th chamber. The keys are stamped LB99335X. This is a lock straight out of a factory box, never installed. Anyone seen this before or know what the X in the key number means?