This is a distinctive design, sometimes known as a "bock" type, for reasons unknown to me.
The squat vertical boiler is 47mm high x 58mm diameter and is tapered. It is a push fit into the square firebox. It has a dummy chimney surrounded by a safety valve, whistle, filler plug and steam feed. The steam pipe goes directly to the side of the engine port face. There is no regulator or lubricator. The original burner is missing but looks as if it should be a round wick type approx 38mm diameter.
The cast engine frame is of a distinctive design, looking similar to some accessories such as a grinder/polisher. It is a rather ornate shape, with the port face near the bottom and the crankshaft between the two arms at the top. The cylinder is a single acting oscillating type, 6.5mm bore x 15mm stroke. The other end of the crankshaft has a 37mm diameter flywheel incorporating a 7mm diameter pulley. In the centre of the crankshaft there is a knurled section which drives a dummy governor, which is held in place by a dovetailed slot in the cast frame.
The whole is mounted on a wooden base, which also has a brass nameplate saying "HERCULES".
As acquired, there were several parts missing broken or non-original. These included the chimney, whistle, burner, governor, crank and pipework. These items have all been repaired and/or replaced. A reproduction dummy governor has been made by a friend. I have a non-original burner which fits.