What crucial security feature was incorporated into Jeremiah Chubb's lock patented in 1818?

Answer

A special lever that would jam the mechanism if tampered with

Jeremiah Chubb introduced the Chubb detector lock, which included a special lever designed to jam the mechanism and signal the owner if any tumbler had been raised incorrectly by a picker.

What crucial security feature was incorporated into Jeremiah Chubb's lock patented in 1818?
Originsecuritymechanismlockkey