I assume this is the device you are interested in David.
It is supposed to be a Simplex with a home built wooden body to give the driver a little protection from the elements.
It is very loosely based on an actual Simplex locomotive that was owned by the Fleet Light Railway and used on their farm. The real loco had a higher body so the driver could stand up when driving.
On the model the body is lower to allow the loco to get under the bridge into the fiddle yard, As in the pictures. On the model my driver has to remain seated not that there is a driver because the vertical motor is where he would sit.
The model is scratch built on a Model Power chassis but is a creature of moods in that it runs better some days than others.