This is one of four sandglasses recovered from the Mary Rose, this being the most complete.
It was found in a personal chest on the main deck, which presumably helped protect it from too much damage, as we still have parts of the glass sand container, as well as the copper alloy diaphragm that regulated the speed at which the sand passed through. While it is impossible to know exactly how long this sandglass was set to measure, it is most likely to have been around 30 minutes, as this was the length of time between bells. Eight rings of the bell made up a shift (or “watch”) on board ships.