Between 1864 and 1958, Queensland Railways ordered 47 types of locomotives for purposes such as freight, passenger and mail train use.
Until 1889, each of the isolated sections of the Queensland Railways adopted its own locomotive numbering system.
With the impending joining of most of the sections, in 1890 a new centralised classification system was adopted to eliminate duplications.
[1][2] The classification system consisted of a letter, indicating the number of driving axles, followed by a number, indicating the cylinder diameter in inches and factions of inches.
This was confusing for two reasons: Where classification numbers were duplicated, the classes were usually distinguished by the name of the builder, e.g. A10 Baldwin, A10 Fairlie, A10 Neilson.