This is the middle of three simple steam engines made by CK Matsutoku. It has a simple oscillating cylinder mounted on the firebox along with the crankshaft and with a base that barely exceeds the firebox in size. It is made mostly of brass, the exceptions being the burner, flywheel and crankshaft. No part of it is painted.
The galvanised steel meths burner has two wicks and a handle, which doubles, potentially dangerously, as a filler and vent. The boiler - 40mm diameter x 95mm long - has a safety valve and a small steam dome. The steam pipe feeds from the dome to the engine frame, which is a thin brass bar riveted to the side of the firebox.
The single cylinder is a basic single acting oscillating type, 8mm bore x 22mm stroke. The crankshaft penetrates through the firebox and has a 43mm diameter lead flywheel on the other end.
As acquired, the safety valve and burner were missing. The cylinder was a plain brass one, which suggests that it could have been one from a Crescent engine. Most CK branded ones are nickel plated. I have since found a safety valve and burner, and a correct nickel plated cylinder.