Matrix codes have been reported on general Nirvana discographies since the late 1990's, but had little use in those days other than to identify the most obvious pressing plants and for counterfeit identification. In the early 2000's this website covered test pressings and Pennyroyal Tea items as today (and had a discontinued section for other interesting items which surfaced, as for a period there was no general discography being maintained), but I was struggling to explain much more about these items other than to show pictures and give the most obvious information. What does this "RE-1" on the pink Bleach test pressings mean, and which company wrote it? What is the deal with this pressing at all? Why are some parts in matrix codes very different to others, such as digital and mechanical text on optical discs? How do they do that and what does it mean? Does the L-codes on many Sub Pop records identify Erika Records as the pressing plant? (It does not!) What do the IFPI codes mean?
At some point around 2006 or so I started learning about vinyl and optical disc manufacturing, to understand the different steps in the process and how the codes are added in each step, and a while later the manufacturing section was launched with the help of industry sources and comparing a very large number of matrix codes. At that time there was not very much similar information about pressing plants and mastering studios, matrix codes in general, on the Internet, and my original intention was to go into detail in a lot of pressing plants. However, this task is too large for one person, and since then a number of online communities have done this very well.
As a result, the information on this website is Nirvana specific. It only brings up information which is necessary to understand official Nirvana releases, mostly from the late 1980's to the early 1990's. Much of the manufacturing information is still general, but something which holds true about a pressing plant or any company from for example 1990 to 1993, may not be valid for earlier and later pressings, and perhaps not even for pressings of different bands or record labels from the same time.
Most of the information which have been obtained from other sources have been gathered conducting e-mail interviews with various industry people, and cannot be referenced in the traditional way. Some of these sources also want to remain anonymous. As a result it is very difficult for you, the reader, to verify the information. My intention with referencing for example "Mayking employee" and "Jim, MCA UK" is to show that the information has come from someone with first hand knowledge of these things, and not deduced nor assumed by myself.
If the reference note is within a sentence, in other words it appears before the period, it only applies to that sentence, or from an earlier reference note in that sentence and to the current note. If it appears after the period, it applies to all sentences so far in that paragraph, or from an earlier reference note in that paragraph and to the current note.
Information regarding vinyl or optical disc manufacturing which is not referenced has been deduced from research into and comparing a lot of matrix codes. If ten discs you know are from Australia say "DISCTRONICS B", and ten from the UK say "DISCTRONICS S", it is safe to deduce that glass masters made in Australia will say "B" and those made in the UK will say "S". (However, without a presence of a mould IFPI, it cannot be known for certain which plant pressed them, as glass masters could have been sent from one plant to the other.) If vinyl records from an unidentified company have identical internal matrix numbers as optical discs from Sonopress in Germany, it is safe to deduce that those vinyl records were also mastered by Sonopress, and as Sonopress also pressed vinyl up until 1992, they were also pressed by them. If records pressed by MPO, but cut by different mastering studios all share the same matrix code pattern with the same handwriting, it is safe to deduce that the matrix codes were written by MPO, and not by the cutting engineers from the different studios (this was later confirmed by one of these cutting engineers).
If you have any questions regarding any of the information presented, please feel free to e-mail me, and I will do my best to explain how the information was obtained or deduced.
1. Postcard from Krist