Tim Hunkin has a neat page with the history of safes and how to crack some of them- An illustrated lecture about the history of Safes and Safe breaking. The lecture is based round a large wooden safe with a video camera inside, projecting the inside of the door mechanism on a screen. This is currently my favourite lecture to perform. There’s something very satisfying about the simple ingenuity of safes and locks. Its also an area of engineering design that has not been transformed by science or maths, and to me illustrates intuitive aspect of the subject, which often now gets forgotten. Link.