A 19th century antique hourglass in a mahogany cage with four spindles. An inner glass bulb filled with sand which takes approximately one hour for the sand to run through. It measures 23cm h x 13.5cm w.
They were made in various sizes for different requirements but the usual length of time was an hour, half hour or 3-4 minutes.
Often used by the Royal Navy up until 1839 to count in half hours and for marines as a dependable measure of time whilst at sea. It has also been documented that these  timers were used in the church pulpit for measuring the parsons sermon to ensure it did not overrun!!