This is the post I put on when I first listed it -
This is the famous Cryptograph Lamp. Drawings exist for Stephenson, Davy and Clanny versions. Made by Archibald of Glasgow in 1822, this is the only known surviving lamp. Totally impractical in a working pit, who would remember all the different codes? Unless they were written on the wall behind the page 3 calendar!
It is an ordinary Clanny Lamp design other than the crytograph locking system. It is acknowledged as being the most desireable of the British safety oil lamps by most collectors and its value is in five figures. It is the only known example, but there must have been more originallly. No one has seen any though or the Davy and Stephenson versions. I have many other rare lamps in my collection, but I do not have sole rights on rare lamps!!!!! I visited another lamp collector last weekend. He has dozens of other rare lamps that I had not seen or heard of. It is amazing how many brass founders had a go at making lamps with different locking devices on, or different air feeds, of different ways of displaying the methene content in the air. They used different burners, fuels, air shut offs, heat wires, different metals, etc etc. always a revelation when you dismantle and inspect a "new" find.
Chuck