During the production run for the TR7 and TR8 (as well as the periods before and after that time), British Leyland (later Jaguar Rover Triumph) assigned each Technical Service Bulletin (TSB) an identifier. The format of these identifiers provided some basic information about the TSB (e.g. the year of issue). Two formats were used.
Pre-1980 TSBs Through 1979, TSB were assigned "Numbers", which were actually alphanumeric identifiers. The format was YY-C-Na, where
YY - The year issued.
C - Indicates the component or area as follows: A - Engine, B - Electrical, C - Body, D - Transmission, E - Paint, F - Chassis, G - Miscellaneous, H - Air Conditioning, and Z - Recalls.
N - A sequential number within each component/area. The first TSB of the year for each component/area starts with 1. Also note that each marque within BL had its own sequence, meaning there were duplicate TSB "Numbers". To illustrate this point, there are three 77-B-1 TSBs - one for Austin/MG (1977 Wiring Diagram), one for Jaguar (Revised Electrical Relays), and one for Triumph (Head Lamp Feed Wire Security).
a - Optional. Indicates an addendum to a previous TSB. For example, 75-D-6A and 75-D-6B are addendums to 75-D-6.
In 1979, BL began color-coding by marque to help with segregating TSBs. Triumph TSBs were printed on blue paper, Jaguar on green, and Austin/MG on light red. TSBs applying to all marques were on white stock. However, the issue of duplicate "Numbers' remained (e.g. there are four 79-A-1 TSBs, with one each for Austin/MG, Jaguar, Triumph, and All Marques). TSB 79-G-1 (note it's on white stock) provides additional info on this change.
One last note for pre-1980 TSBs. There is nothing in the "Number" to indicate which model within a marque is being addressed by the TSB. Under Triumph chassis TSBs, the first bulletin of 1975 (75-F-1) was issued against the TR6, with the second (75-F-2) for the TR7, while the third (75-F-3) applied to all Triumph models.
1980 and later TSBs The color coding which began in 1979 carried over into 1980 with the following changes.
Austin/MG was now just MG and used pink paper.
White stock was used for administration. This was in place of the all marques nomenclature in '79..
Rovers TSBs were added on tan paper.
Starting in 1980 the "Number" used in the previous years was now known as "Item". "Item" could be in one of two formats as follows.
MYY/NNN was used for marque-specific TSBs, where
M - Indicates the marque with J for Jaguar, M for MG, T for Triumph and R for Rover. While these may seem redundant when combined with the color coding being used, it would help in those instances where a 'Xerox' copy would be made on white paper.
YY - The year issued.
NNN - A sequential number within each marque. The first TSB of each year begins at 1.
YYA/NN was used for administration TSBs, where
YY - The year issued.
A - Indicates an administration TSB
NN - A sequential number that begin with 1 for each year.
The component indicator was no longer being used, with TSBs being organized strictly by marque (or administration)..
Another change, though not officially noted, dealt with the number of TSBs per page. Before 1980, no more than one TSB was listed on a page. With the latest changes, a single page could contain two, three, or even four TSBs..