This series was artificially created to regroup technical drawings and cartographic material transferred on distinct occasions over more than two decades and which, until recently had not been organized.
Sub-series 1 to 4 contain technical drawings which could easily be segregated by builder or operating company and then regrouped by country.
Within the first four series there is a very clear focus on the Toronto, Hamilton and Buffalo Railway Company and it's parent companies, the Canadian Pacific Railway and New York Central, their successors, predecessors and affiliates. In addition, there are drawings concerned with Merrilees' business interests and other drawings whose provenance or use could not be ascertained.
Many of the drawings belong to sets originally created, gathered or maintained by the T.H. & B. for the assembly or maintenance of rolling stock and steam locomotives. Andrew Merrilees quite likely acquired these sets after steam became obsolete on the T.H. & B. It is not impossible he may even have used some of them in the course of his business activities. Numerous creators are represented, including the company's own engineering offices but also makers of material used on the T.H. & B. or even former owners of rolling stock eventually purchased by the railway. Additional materials were acquired by Merrilees during the course of his research. In all, some 175 Canadian, United States and foreign railway companies or railway equipment makers are represented. In addition there are many drawings signed by Andrew Merrilees (or which can be attributed to him) which appear to be essentially tracings of damaged originals by other creators. A high proportion of these drawings relate to lettering used on cars of various companies.
Abundant annotations provide information as to the numbering of engines and railway cars, as well as to types of locomotives.
Sub-series 5 includes an impressive selection of booklets of diagrams of locomotive or rolling stock used on a specific railway company. These booklets often include basic technical data and dimensions. Some 145 booklets are complete while 23 others have substantial gaps, there are also a fair number of loose sheets. To these booklets are associated rosters of engines and rolling stock, some in booklet form, either prepared by the companies themselves or by researchers, possibly even by Andrew Merrilees himself.
Sub-series 6 includes maps and various printed matter re. locomotives and rolling stock but obviously not prepared by railway operators or equipment makers.
Sub-series 7 is used for railway related material that did not appear to be the creation of railway companies for operational purposes but rather by railway enthousiasts.