The Vickers Range Clock was a clockwork device used by the Royal Navy for continuously calculating the range to an enemy ship. In 1903, Percy Scott described a device he'd invented which was similar to the Vickers clock. In April 1904, Vickers worked with Scott and patented their device, samples of which were available for trials in 1905. In 1906, the Royal Navy ordered 246 units for use on their ships. More than one might be installed, to allow for tracking multiple targets.