I get confused easily by all this horsepower calculation and don’t know if it has anything to do with stationary engines, but Sipps were built at the time when traction engines were rated in nominal horsepower and Stuarts were built when they were rated by brake horsepower, for example a 110HP Case was known as a 32HP pre 1910. I also don’t know if being built in the UK changes that for the Stuarts…
And to add to other’s comments, I wouldn’t worry too much about it Mike, that is an engine any of us would LOVE to own!!