The pre-war (1937) version of the SE1 is very similar to the 1946 version, with only minor differences. The engine casting does not have the name Mamod cast into it, and the exhaust is not fed to the dummy chimney,
The boiler is heated with a two wick meths burner. The boiler is 1 3/4" diameter x 3 3/8" long. It has a safety valve and a compression fitting for the steam pipe. There is no water level indication and the dummy chimney is mounted on the base.
The steam feed pipe goes directly to the back of the cast brass engine frame, with no regulator or lubricator. The single cylinder is a single acting oscillating type; 5/16" bore x 9/16" stroke. The short piston rod connects to a 1 1/4" diameter (mazac?) disk crank, which also acts as a flywheel. The crank shaft passes through the frame casting with a small brass pulley on the other end. Exhaust steam is not fed to the chimney, which is purely cosmetic.