Hidden away on the run-off area of a vinyl record - - whether it is a 7" single or 12" album - is a wealth of information relating to the life cycle of the recording on the disc and of the disc production itself - if you look very carefully! First though it is important to understand the life cycle of a recording from performance to final production of the disc.
The original performance by the artist in the studio was recorded onto a master magnetic tape. This was transferred (‘cut’) onto an Acetate disc. This acetate disc was generally a single sided disc with a metal base and soft nitrocellulose lacquer. Although 'playable' these discs would wear very quickly - a matter of two or three plays could rendered them useless - so a Master Disc (which was actually a ‘negative’ of the recording) was produced from this Acetate and, depending on how many records were expected to be needed, Mother Discs were then manufactured. Stampers were produced from the Mother discs and these were used in the pressing machines to actually produce the vinyl record. As each stamper started to wear out another was produced from the Mother. As Mothers wore out new were produced from the Master. When a Master was worn another was produced from the original acetate disc.
All these various stages of production were allocated unique reference numbers. The masters and mothers were each given a sequential number. The Stamper number was in code form, the code being the word GRAMOPHLTD whose letters represented the numerals from 1-10, so for example the first stamper produced would be given the code letter 'G'. The 13th stamper produced would be given the code 'GA'. In theory the first album off the presses would have a mother code of '1' and a stamper code of 'G' although large runs may have had several presses running at the same time with different stamper numbers. It is also worth noting that due to different stamper wear rates it is not uncommon to find different stamper codes on each side of a disc.
These codes and sequential numbers are known as the matrix information and appear on the vinyl run-off. They can be difficult to see but can be found spaced around the label at 90 degree intervals.
In the example shown here (a 7" vinyl single) this disc was pressed from (left) the first mother and (right) the first stamper (G). The matrix number on the lower part of the disc - 7XCA 32053-1 indicates that the record is a 7" single mono recording (7X) with a unique library reference of 32053 using the first master (-1). A stereo recording would have the prefix '7Y'. In the case of a 12" album there is a slight difference. For example should the matrix read XAX3642-1 then this would indicate that the record is a 12" LP mono recording (XAX) with a unique library reference of 3642 using the first master (-1). A stereo recording would have the prefix 'YAX'.
Finally - why is this all information of use or interest to collectors? Many collectors prefer to have early copies of albums (first master, mother and stampers) although the real value of this is hotly debated by vinyl enthusiasts.