This is an early flat base example of the single cylinder MM2. The first version of the MM2 was a twin cylinder horizontally opposed type but few of them were made and are now very rare. The model was reintroduced in 1948 with a single cylinder so that it became similar to the slightly smaller MM1 which was updated about the same time. This is that version. It has the plain flat base common to all Mamods of the era.
It is an overtype engine with everything mounted on top of the 1 3/4" diam x 4 3/8" boiler, including the 5/16" diam x 3/4" stroke cylinder, 1/4" safety valve, 2" diam spoked brass flywheel and the purely cosmetic dummy chimney, which doesn't even cary the exhaust steam. It has a two wick meths burner.
As acquired, it was in very poor condition; very rusty with very little paint left and with the piston and burner missing. I had a correct sized piston in my spares box so I did a quick repaint before the rust got any worse. I also replaced the rubber feet and the boiler strap. I'm not sure if the safety valve is the original but I've kept it as it is, just replacing the seals.