by maxxed » 13 May 2006 2:02
The B&S locks used in the early GM's were a wafer lock. The wafers have a notch in the side that the placement of determines the depth of the cut on the key. When all of the notches are lined up with the back of the sidebar, the sidebar will retract allowing the plug to turn. Go to an auto wrecker and remove a door lock from a 70's or 80's GM, and see for yourself.
I don't know any real history of the development of the sidebar lock, maybe a patent search can help.