BRITISH NAVY DEPTH CHARGE FUZE SETTING DEVICE

As I have been told (I have never seen one before) by an old time collector that this was part of the device that took the Depth Charge off safe and set the depth that it would explode. This bronze outside threaded disk measures 2 5/8” in diameter and has settings for Safe then depths of 50, 100, 150, 250, 350, and 500 feet to set the explosion. The safe area has a hole cast in the disk that I would believe is part of the safety mechanism. Condition near mint