There is no maker's name or trade mark visible in this engine but I've been told, by someone who knows about these things, that he's 99% certain it's made by CK in Japan. It is a nice V-twin with a vertical boiler on a wooden base. There is also a horizontal boiler version (see here)
The boiler is a vertical type with a central flue. It is made of brass and has a seamed joint construction. It is 55mm diameter x 76mm high. There is a whistle, safety valve and steam connection on the top around the chimney.
From the top of the boiler, the steam pipe feeds, via a T connection, to the backs of the two port faces. The cylinders are simple single-acting oscillating cylinders, mounted in a V configuration, about 120 degrees apart. This is not the ideal configuration for a twin cylinder but it works ok. Cylinders are 8mm bore x 22mm stroke. Both piston rods are connected to a common crank. At the other end of the crank shaft is a 55mm diameter flywheel, which has a groove in it's rim for a drive belt. I don't know, at this stage, how much torque this engine generates but I guess a rim drive may be a bit optimistic! There is no other pulley provided.
As acquired, it was in poor condition, with several loose/damaged parts and evidence of limescale deposit around the steam pipe connection (suggesting a possible leak). The burner was not original and looked home-made to me. The bottom photo on the left shows the engine in it's unrestored state.
I have resoldered most of the steam joints, including the whistle bush, which wasn't leaking but was on upside-down! I replaced the nails holding the boiler with screws and resoldered the brackets to the firebox. I cleaned up the brasswork but did not polish it. I re-varnished the wooden base and replaced all the wood screws.