Riches and Watts advertised using catalogues with engraved plates illustrating their products, fortunately a few of these catalogues have survived, enabling us to deduce some of their history and the development of their products.
This is where it becomes a little confusing. The 2½ nhp engine preserved here was part of a combined engine and boiler unit, the engraving above is of the combined plant but showing the 1 nhp engine from their 1875 Catalogue, note the overhung (or as they called it the 'single dip' crank, the larger engines such as our 2½ nhp had a double web or 'double dip' crank. This is the only illustration so far found which shows the style of A frame casting which our 2½ nhp engine has, all the later engines shown (and the recently acquired 1 nhp 'stand alone' engine have strengthening webs where the A frame bolts to the bedplate - presumably as a result of earlier engines cracking their frames at this point which is a considerable stress raiser.
This engraving is of the earlier pattern of 'stand alone' 1 nhp engine, ours is missing it's governor and throttle valve but these can be re created using parts from the 2½ nhp engine as patterns.