Hold the record at a shallow angle under a lamp and turn it slowly. The characters catch the light. Both sides have their own.
What is the matrix or runout number?
It's the record's manufacturing name, written by the cutting engineer.
A record starts as a lacquer, an aluminium disc coated in soft nitrocellulose, cut in real time by a lathe. While the lathe is running, the engineer scribes the matrix into the blank outer band. That lacquer is then electroplated to make a metal father, the father makes mothers, and the mothers make stampers. The stampers are the metal parts that press the vinyl. Everything scribed into that first lacquer travels down the whole chain into every copy.
Some plants added their own marks at the plating stage, stamped in with metal type rather than scratched by hand. That's why one runout can hold two kinds of writing: flowing hand-etched script from the cutting room, and blocky machine-stamped characters from the plant. Learning to tell them apart is half the skill.
How do you read a matrix number?
Read it in four parts: the side identifier, the cut number, the stamper and mother codes, and the signatures.
The side identifier
Most matrices name the side. Sometimes that's a plain A or B. Often it's built into the master number itself, so a UK EMI album might carry XEX 421 on one side and XEX 422 on the other, sequential numbers issued by the company for that release. The XEX prefix marks a mono LP master, YEX a stereo one. Other companies used their own prefixes for the same job.
Always note which physical side each code came from. A runout string is close to useless if you can't say whether it was side one or side two.
The cut number
A trailing digit after the master number is the lacquer or cut number. A -1 is the first cut of that side, a -2 a recut. Lower is usually earlier, though a recut can be ordered the same afternoon (a fault on the first lacquer) or fifteen years later (a new run from an archived tape). Treat a low cut number as evidence, not proof, and confirm it against the label and first pressing markers.
You'll also see the same side cut in different rooms, giving completely different numbering styles for one album. That's normal for anything that sold well.
Stamper and mother codes
These are the plant's own bookkeeping, and they're the most granular thing on the record.
EMI encoded them as letters, using the word GRAMOPHLTD as a cipher: G is 1, R is 2, A is 3, M is 4, O is 5, P is 6, H is 7, L is 8, T is 9 and D is 0. A run of letters after the matrix decodes to the mother and stamper numbers, so collectors can say how deep into a run a given copy sits. Other companies used different code words and different systems, but the principle holds everywhere.
American plants left their own fingerprints. Monarch in Los Angeles stamped a delta symbol followed by a job number. Columbia's plants at Terre Haute, Pitman and Santa Maria each marked their work. British pressings can carry plant marks for Hayes, Orlake, Damont or Lyntone. If a code looks like nothing on the label, it usually belongs to the plant.
Mastering engineer etchings
Cutting engineers signed their work, and those signatures are the most enjoyable thing in any runout.
- George Peckham etched "A PORKY PRIME CUT" or "PECKO" across a large share of British rock records.
- Robert Ludwig signed "RL", and Sterling Sound and Masterdisk stamped their studio names.
- Bernie Grundman's rooms mark "BG", Kevin Gray's cuts carry "KPG", and Wally Traugott signed Capitol cuts "Wally".
Some are jokes, greetings or messages to the pressing plant, scratched in by hand because the engineer knew someone would eventually read them. Those are worth writing down too.
Why do two identical-looking pressings differ?
Because a stamper is a consumable part. A metal stamper presses on the order of a thousand copies before the high frequencies start to soften and it gets swapped for a fresh one off the same mother. A record that sold in the hundreds of thousands went through dozens of stampers, several mothers, sometimes several lacquers, and often more than one plant.
So two copies with the same label, the same catalogue number and the same sleeve can be genuinely different records. Different cut, different tape generation, different plant, different point in a stamper's life. Early stamper copies of well-known titles get sought out for exactly this reason, and the runout is the only place that difference is written down.
The other common cause is a reissue reusing old artwork. The sleeve says 1971 and the label looks right, but the runout carries a 1980s plant's marks, or a machine-stamped code style that didn't exist yet. The dead wax is harder to fake than the front cover.
How should you note your matrix numbers down?
Transcribe them exactly, character for character, including spaces and stray symbols, and note which side each string came from.
A few habits make this quick:
- Photograph before you transcribe. Hold the record at an angle to a single light source and take one photo per side. Reading from the photo beats squinting.
- Copy it literally. Don't tidy the spacing, expand abbreviations or drop odd characters.
XEX 421-1N ⊥ G Rshould go down asXEX 421-1N ⊥ G R. - Mark stamped versus etched. A short note like "stamped" or "hand-etched" carries real information about which stage of the chain left the mark.
- Do both sides. Sides get separated in reissue programmes more often than you'd think.
- Record it the day it arrives. A runout you meant to check later is a runout you never checked.
Cratemint keeps that string with the record, in the private notes on your own copy, alongside what you paid and any condition detail you want to remember. It stays with your pressing, so it's there the next time you're comparing your copy against a listing. When you're grading the record as well, vinyl record grading explained covers the scale sellers use.
Cratemint is free on iPhone. Every feature, for everyone.
Common questions
What is the matrix number on a record?
The matrix number is the code cut or stamped into the dead wax, the smooth band between the last groove and the label. It was put into the lacquer at the mastering stage, so every copy pressed from those stampers carries it. It identifies the master and the side, and it usually carries a cut number too.
Where is the dead wax on a vinyl record?
The dead wax, also called the runout or the runout groove area, is the ungrooved ring between the end of the music and the paper label. Hold the record at an angle under a lamp and turn it slowly, and the etched and stamped characters catch the light. Both sides carry their own codes.
What does a Porky Prime Cut mean in the runout?
It's the signature of the British mastering engineer George Peckham, who often hand-etched 'A PORKY PRIME CUT' or 'PECKO' into records he cut. It tells you who cut the lacquer, which in turn tells you a lot about where and roughly when the record was mastered. Collectors use engineer signatures like this to separate pressings that look identical in the sleeve.
Why do two copies of the same record have different runout codes?
Because they came from different cuts or different stampers. A lacquer is cut, plated, and used to make stampers, and each stamper presses a limited number of copies before it wears out and gets replaced. A busy title needs many lacquers, many stampers, and sometimes several plants, and each of those leaves its own mark.
What does the number after the matrix mean?
A trailing digit is normally the lacquer or cut number for that side, so a -1 is the first cut and a -2 is a recut. Lower is usually earlier, though a recut can be ordered years later or on the same afternoon. Letters that follow it are typically mother and stamper codes from the plating chain.
Does the matrix number tell you what a record is worth?
No. The matrix identifies which pressing you have, not its condition or its price, and condition is what collectors weigh most heavily. Use the runout to establish which run your copy came from, then grade the record and the sleeve separately.