Curious question for anyone who may know. Who first invented the first security pin and when? I know it was Yale Lock Company, however, I am curious of an exact whom?
Could try looking up the patent online. Patents are always in the name of a person (or people), although they are often assigned to a team, so even if it was assigned to Yale the inventor would be listed.
I've been up and down through the patents, so far the earliest thing I can find is for this mushroom pin... it is making me believe that the mushroom was the first of the breed.
If you are interested in this sort of thing you might enjoy Graham Pulford's High Security Mechanical Locks. If I remember correctly, he goes into the history behind some lock developments.