From quite an early stage some regions gave DMUs set numbers, and the use of these spread over the years. By the time of the last 'big' passenger withdrawals, these 101s were known more by there set numbers that by vehicle.
There has been variations on how these set numbers have been carried over the years.
Set numbers first began appearing late in 1959 in the form of a plate fixed in clips on the solebar of WR cars. An example is shown on W50124, and these were centred above the leading bogie on both sides of the power cars.
The enamel plates measured approx. 9x2 inches. CAT was Cardiff Cathays, RDG was Reading, SHL was Southall. Other codes used were CDF (Cardiff Canton), BL (Bristol) and TYS (Tyseley). The number series for suburban sets was 3xx (116s) and 4xx (117/8s), and Cross-Country sets were in the 5xx series. The Cathays, Reading and Southall plate images are courtesy of James Hyde and Simeon Gaskell.
The empty clips can be seen in the image of W50100, which is also carrying a cast shed plate (84E / Tyseley).
The Western Region seemed to keep thier vehicle together in their set formations more religiously than other Regions. Some depots elsewhere seemed to change the formations almost daily, whether they carried set numbers or not.
In mid-62 set numbers started appearing in the left cab window of the Tyseley sets instead of the solebar plates. These were much easier to see, and were black numbers on a white board.
These would continue in many forms over the years, and the next image shows a later type from Tyseley (now a LMR depot), the two letter depot codes were added in 1969. These boards were never permanently fixed, being held in place by clips.
The ScR seems to be the next Region to assign set numbers in 1966, and seems to be first application to be marked onto the cab. The numbers were applied by stencil. This article gives more detail on their introduction.
In time these were instead applied with black stickers using the same number series.
In the 1970s set numbers also appeared on East Anglian sets in the xx series, and these were often fixed to the upper cab windows.
When the set numbers were applied to the cab front of Western Region sets in the blue livery period they carried a prefix denoting their operating region: L - London; C - Cardiff; P - Plymouth; and B - Bristol. At first these stickers were in a Gill Sans font (the font used for labelling in green livery) even though Rail Alphabet was now the norm for blue livery. Later on LMR sets would also adopt the prefix system, using either one or two letters, and denoted the depot of allocation rather than the operating region.
In 1981 ScR sets began carrying set numbers which also denoted the class of the set. The following number series was the first used (often the same final three digits as the set was already carrying): 101 3xx; 105 34x-37x; 107 43x/44x; 116 38x/39x and 126 4xx. Class 122 55002 was carrying set number 101.
Network South East sets continued to use the WR single letter prefixes where set numbers were carried. Regional Railways sets would carry class prefixes. Departmental stock would also be allocated set numbers, in the 960 xxx series.
The following pages provide a sample of the set formations to be found over the years.
East Anglia 12/85
East Anglia Summer 1986
LMR Summer 1986
Buxton 108s 1988/9
ScR February 1981
ScR Summer 1986
ScR August 1986
South Wales 1987
WR December 1982
WR Summer 1986
NSE November 1992
NSE November 1993
Regional Railways Nov. 1992
Regional Railways Nov. 1993