Solid brass with glass lens, 3" X 5.5". Patterned after a brass original which was installed vertically on a locomotive's firewall, angled upwards so that the standing Engineer could view the time while still driving. The large oversize key allowed him to wind or set the clock with heavy gloves on. Re-purposed in the same size as the original, ours is intended to be placed horizontally on a table or desk. Accurate quartz movement uses one AA battery (not included).