Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Just from examination, it appears to be most of a speed control device for a large, belt drive engine of some sort.  The flat belt would have spun the governor, lifting a now absent arm, with a plunger inside the now vacant cylinder. The round dial and index scale on the frame indicate speed, perhaps in rpm’s, or linear feet of belt in a minute?    What it’s part of is a mystery, but it apparently was plunked on a plinth for your viewing pleasure at some time in the past.

The shapes of the no longer mating bits hint at what ought to be there.