That's a Big Beauty you have there Philip ... for certain and for sure!
I'd say it is comparable to a 1/4 horsepower Sipp and thus fully capable of doing real work. In that way I'd say that it actually is a full size engine in that engines of this size were often used to power things within shops and factories back when steam was King. This engine could easily have driven a bellows on a small forge or a bank of sewing machines, possibly even a small lathe or drill press, or a whole host of smaller machine tools.
NICE!!!