Moving magnet galvanometer with dial inscribed "Greenwich Mean Time", made by Hunt and Roskell Limited, Clerkenwell, London, England, 1843-1897. The face of the instrument reads: 'This needle is deflected precisely at each hour, Hunt & Roskell Ltd, jewellers and watchmakers'.

The principle way time was distributed in Britain in the nineteenth century was by telegraph, and some of the large clock and watchmakers displayed a galvanometer in their windows to provide a time service for passers-by. These timepieces could be set accurately with a simple indicator worked by time signals telegraphed from Greenwich.