All coal miners lamps in the UK were required to have magnetic locks so they could not be opened underground. These are parts for miners lamp lock parts.
The miners lamp magnetic lock spring holds the locking pin in place and can only be withdrawn with a strong magnet. Traditionally this was a large horseshoe magnet within a metal case bench mounted in the Lamp Room. Nowadays we use small rare earth magnets. Magnets cannot be taken underground as they could open a lamp, which is not allowed or they can cause sparks if dropped which can cause an explosion.
The lock is in a brass casting on the side of the fuel vessel. The bung fits into a threaded hole at the base of the lock body and it retains the spring sold here and the locking pin. When fitted by us to a lamp the slot on the head is removed so it cannot be unscrewed. These are often drilled out to remove the locking pin. The magnets we sell are placed on the base of the lock body and pull down the spring and pin allowing the fuel filler flap/locking plate to be opened.