I believe this to be a scratch built engine /boiler combination from about 1870-1890 , with later pressure gauge. It runs very smoothly on incredibly low pressure, it includes a water pump to refill the boiler, although I haven’t used this feature myself. It is fired by a blow lamp or similar inserted into the flame tube . It measures approximately 14 x 10” . The flywheel measures 4.25” . It came from an auction in Frome about 4years ago and was part of a very prestigious private collection of steam engines, some of them fetching many thousands of pounds, I was lucky to secure this for £600 and I have enjoyed having on display in my house. The history of the engine is unknown , I took it to my local steamers club who gave their opinion as to its origin.
eBay