bczrx,
We're in the world of shotgun parts nomenclature, and maybe even worse, the realm of British/Spanish shotgun parts nomenclature. This is a place where words may sound like American English, but they really aren't.
In this world a 'pin' is a screw. The number of pins in a lock is the number of screws used to hold everything together.
People try to count the number of pins in a lock by looking at the outside of a lock and counting the number screw ends visible. Most folks will do this because they won't, for any of a host of reasons, take the lock off the receiver and look at the inside of the lock plate.
This actually works pretty well for most locks, but the wheels come off that approach when the lock maker blinds the pins. A 'blind pin' is a pin that has a screw hole that doesn't go all the way through the lock plate. Such pins are not visible on the outside of the lock plate. Blind pins are commonly done to give the engraver an uninterrupted lock plate upon which to execute his art, but may be done just because the lock maker feels like it.
Watch for a PM; I'll send you some lock related stuff.
