The drawings to the right illustrate the GRS compound lens style searchlight signal.  This signal is very similar to the US&S H-2 style searchlight signal.  Both have a compound lens design with a smooth non-prism outer lens.  They both accommodate this design by adding a front housing extension.  The housing extension of each signal also contains an adjustable close-up deflecting prism lens and a cover to access this lens.  The GRS signal attaches the cover with standard bolts, while the US&S signal uses bolts with wing-nut like tops.  The signal in the top drawing has a top of mast mounting assembly.  The lower drawing illustrates the elegant GRS side of mast mount.

GRS searchlight signals do not use “D” shaped washers on the front adjusting bolt, instead relying on a nut having rounded over edges.

While the sighting device appears similar to the device used on the US&S searchlight signals, there are a couple of differences.  The GRS signal uses a glass with a painted cross in the front standard whereas the cross in the US&S sighting device has no glass and consists of two heavy gauge wires.  Also, the factory adjustment is made on the GRS sighting device by loosening and moving the glass plate containing the cross on the front standard, whereas with the US&S sighting device, the adjustment is made by loosening and moving a metal plate which contains the pinhole on the rear standard.  Finally, the GRS sighting device is fitted onto studs extending out of the top of the housing and attached with two nuts, while the US&S device is simply attached to the top of the housing with two bolts.

Above.  The nuts shown in the drawing on the mounting stud would be removed before the stud is inserted into the mounting bracket.  Once the stud is inserted, the nuts would then be screwed onto the stud to secure the signal to the bracket.

Left.   Side of mast mounted GRS SA stepped lens style searchlight signal.  Note the absence of the housing extension. 

To open the rear door of the GRS searchlight signal, a flanged nut securing the latch hook is loosened with a wrench-like handle.  Once loose, the wrench is then used as a lever to disengage the hook from a catch mounted on the top inside of the housing.  The US&S searchlight signals use a standard nut with a hinged handle welded on which performs similarly.

The back door seal is made from a rope like material which would be impregnated with wax to protect against moisture penetration.  US&S searchlight signals use the same type of gasket.  Gaskets on modern or upgraded units are made from neoprene, a synthetic rubber-like material used widely in automotive door seals.