For instance, there were the BR (adapted from the LNER system) and LMS carriage codes, which indicated interior layout or usage.
The Great Western Railway (GWR) identified some of their non-passenger carriages and wagons through a series of animal designations, including sea life for departmental (non-revenue earning) stock, followed by a letter for detail differences, e.g. Beetle A.
The majority of the sections below deal solely with carriage and wagon numbering series, though where a particular classification system was used this is also described.
Former 'Private Owner' wagons, owned by industrial concerns rather than the railway companies, had a prefix letter "P" but were renumbered into a new series commencing at 3000.
Some carriages and wagons built by British Railways to the designs of the 'Big Four' companies were numbered in their series and carried the appropriate letter prefix.
New carriages had no suffix: when Pullman Company carriages were added, their numbers carried both prefix and a suffix (indicating regional allocation), as did the 2 tier car carriers built for the East Coast services.
[1] Numbers 100000 to 999999 were used for non-passenger rated stock (including wagons, vans and departmental (non-revenue earning) carriages), while internal user vehicles (stock used for internal purposes (e.g. stores) at specific locations and unlikely to move) took numbers in the 0xxxxx series.
From 1986, those carriages in the 99xxx series which otherwise duplicated BR bullion and exhibition van numbers were renumbered, and from then on the prefix was not essential for identification.
Most departmental and internal user vehicles are converted from revenue-earning stock; only a small number are built for non-revenue earning use.
Initially stock inherited from the 'Big Four' companies was given regional prefixes (e.g. DE, DM, DS and DW) indicating their origin, and adapting existing number series.
Nowadays almost all stock is air-braked, but when TOPS was introduced there was much greater variety, which made marshalling trains more complicated and this information essential.
The letters were: For hauled passenger carriages ('A' series), the suffix denoting the braking arrangements was replaced by two characters as follows:[1] This resulted in a 4 character alphanumeric TOPS classification, such as AB21 representing a Mark 1 Brake Corridor Second (BSK).