Matrix number
Matrix numbers is a term used by record collectors to describe the alphanumeric codes scratched or stamped into the run-off groove area of a gramophone record.
During the process of mass producing records, standard codes are added to the master disc (or matrix) that systematically describe a particular mastering of a particular recording. The cutting engineer may occasionally augment these factory codes by scratching additional personal messages in the run-off groove area, thus "signing" the master disc.
Since the same unique identifying codes are present on every mass-produced record derived from a particular master disc, matrix numbers can be used to definitively identify an example of a particular recording as belonging to a particular pressing, without having to physically play the record in question.
Record collectors have extended the term "matrix numbers" to apply to the identifying factory markings found on any recording media format, such as the alphanumeric codes printed around the centre of compact discs.