Stevens & Co signals have been widely used by many British Railway companies from the 1860s onwards. The original lower quadrant arms in this pack are still in use on British preserved lines and on overseas railways, and a few of the original lattice posts modernised with upper quadrant arms (SN12/2) are to be found on Network Rail.
The early signals used slotted posts with pear-shaped spectacles showing only a red light, which when moved with the arm displayed a clear white light beneath. Some slotted posts (with modified arms and dual spectacles) survived on BR till the mid-1950s. Ex-North British signals still used the pear-shaped spectacle well into BR times, mounted on lattice posts. The H&BR used the same components as the LSWR, with the exception that the finials were painted black and the spectacle had a thicker rim to provide a counterbalance to the arm. Caledonian signals were unique in having a slotted motion plate to allow the spectacle to be slewed in relation to the lamp for viewing around curved tracks, which abounded in the Highlands.