This neat little engine was sold by Chronos Engineering Supplies who describe it as the "Bittleston Steam Engine". It was made by Bittleston Ltd, in a single batch of 1000, to show off the capabilities of their automated equipment. Some were given to key customers and some to Chronos for resale.
It is 100% machined metal construction. The cylinder and pipe fittings are brass. The flywheel is chromed steel. The rest is all blackened steel. It is very solidly built (overall height is only 2 3/4" but it weighs nearly 12 oz!).
The single acting oscillating cylinder is 1/4" bore x 1/2" stroke, the bore being drilled into a 1/2" square block. The flywheel is 1 1/4" diameter and 1/2" thick; solid apart from 4 holes.