This collection comprises 267 engineering plans which date in the main from the mid 1860's to the mid 1880's, plans with later dates appear to be later copies or tracings. They are working engineering drawings consisting mainly of general plans and plans of the component parts of larger engines. Most are of Steam Hammers of various sizes and designs, these being the company’s main business, but the collection also includes a stationary steam engine, a machine house and a travelling crane. Each plan has its own number ending in F, which appears to have been added at some point early this century in a later reorganisation, during which several plans appear to have been re-backed and repaired or replaced by later copies. This renumbering follows a general chronological pattern, but unfortunately is not consistent with earlier plans often following plans of a later date. From notes written on some plans it is clear that they were in use as late as 1949.