This is a version of the Beam Engine without a boiler and mounted under a glass dome. It was originally offered either ready made or as a kit, back in the 1990's and the dome was offered as an optional extra. I bought this one in 2011 and appears to have been supplied ready made around 1994.
The steam feed and exhaust pipes are fed through the base so that the engine can be run on compressed air while under the dome. A 6psi aquarium pump was offered as an option. I assume it could also be run on steam from an external boiler but I guess the inside of the dome would quickly get steamed up from leakage.
The engine is almost identical to this one here where technical details can be found. An interesting difference is that the configuration is a mirror image!