What specific contribution is attributed to Linus Yale Sr., the father of Linus Yale Jr.?

Answer

Developing the first successful pin-tumbler lock in 1868.

Linus Yale Jr.'s father, Linus Yale Sr., was instrumental in developing the first successful pin-tumbler lock in 1868.

What specific contribution is attributed to Linus Yale Sr., the father of Linus Yale Jr.?
inventionsecuritymechanismlockdoor