Internal flue butane fired, regulator is visible on the dome and was originally fitted with a large plastic knob like the one on the butane regulator. Slip eccentric reversing by the unique and unusual arrangement visible on the return crank on the rear driver. The butane jet is also unique in that the orifice is connected to a small piece of angle that is mounted just a few millimiters from the backhead, and the jet shoots from the orifice across an open gap, then into the flue. Lubrication is accomplished by removing the silver cap on the dome and filling a small reservoir with oil. It's basically a one-time lubrication scheme because the reservoir is quite small. It has a humungous pressure gauge! This is one of the steadiest runners I have ever seen, and is quite powerful. The burner can be turned down to where it is inaudible and still steam freely. Quite a shame that these are no longer available. I have seen black, green, and blue Anna's. There's a few great shots of Anna in Marc Horovitz's "Introduction to Small Scale Live Steam". -Richard