This is a sterling silver model of a Davy lamp, which was presented to Queen Elizabeth II in 1958:
The Davy lamp was invented in 1815 by Sir Humphry Davy and is a safety lamp for use in flammable situations. Miners used it in coal-mines, because it did not ignight methane and other flammable gasses.
This lamp was presented to the Queen on her visit to the Rothes Colliery, Scotland - she was the first monarch to visit a coal mine and go down one. The silver lamp is now displayed as part of the Royal Collection.
(When Prince George comes to the throne, he'll be the first monarch to be descended from a coal miner, through an ancestor of his mother Kate Middleton).