The Mamod SP5D is similar to the later version of the SP5, but fitted with a dynamo and light fitting.
It has two single acting oscillating cylinders. This version does not have any reversing mechanism; presumably so that it can safely be fitted with an LED bulb if desired. It is, however, supplied with a traditional incandescent bulb. On the boiler are a safety valve and a filler plug. The characteristic SP series chimney is a dummy. The burner is a plain tablet type tray incorporating a chromed guard and plastic end to the handle. The steam feed has no superheating or lubricator but has an in-line regulator. The horizontal brass boiler rests on the firebox, held in place by the shaped ends of the firebox. The Base is a pressed steel example.
The boiler dimensions are 1.75" diam. x 6" long and the cylinders 5/16" diam. x 3/4" stroke. The colour scheme is typical of the SP series with a red base, blue engine frames and black firebox. The flywheel spokes are also red. The boiler and the cylinders are unpainted brass.
The engine flywheel is belt coupled to a small dynamo which is wired to a 1.25V bulb in a plastic fitting mounted on the base.