Matrix and Runout Numbers Explained (Vinyl and CD IFPI Codes)

The runout (or dead wax) is the smooth band of vinyl between the last track and the label, and the matrix number is the code etched or stamped into it. Together with other marks in that area, such as lacquer, mother and stamper codes, mastering engineer initials and pressing plant symbols, it tells you which cut, which plant and often which pressing your copy is. On CDs the equivalent codes sit on the clear inner ring around the hole, including the IFPI mastering (L-code) and mould codes.

Reading these codes is the most reliable way to tell otherwise identical releases apart, which is why Discogs records them for each release.

What the runout (dead wax) is

Every side of a record ends with a lead-out groove that runs into a closed loop near the label. The flat vinyl in between is the runout area. Wikipedia lists the other names you'll hear: run-off groove area, end-groove area, matrix area and dead wax.

Plants and engineers used this space for production information never meant for the buyer: which side it is, which cut, which metal parts were used and where it was pressed. That same information is what collectors use to identify pressings.

How a record is made, and why there are several codes

To understand the codes, it helps to know the chain of parts:

1. Lacquer (acetate) – the mastering engineer cuts the grooves into a lacquer-coated aluminium disc. The matrix number is usually scratched into this lacquer by hand.
2. Master (father) – the lacquer is electroplated to create a metal negative.
3. Mother – a positive metal copy grown from the master, so one cut can yield many sets of stampers.
4. Stamper – a negative made from a mother and fitted into the press. Stampers wear out and are replaced from the mother; worn mothers are replaced from the master.

Because each stage can be numbered, one side of a record may carry several separate codes. On many UK pressings the matrix, mother and stamper marks sit roughly 90 degrees apart around the label.

Matrix numbers and cut (lacquer) suffixes

The main matrix number often repeats or relates to the catalogue number, with a side indicator. A suffix after it, such as -1, -2 or 1A, usually marks the cut. In a typical example, a number ending -3 is the third cut of that side.

Sides were re-cut for several reasons: worn or damaged stampers, technical faults, production at another plant or in another country, and reissues. That's why a -1 is a clue, not proof of a first pressing. Wikipedia notes that a first cut may have been rejected, and the "Secrets from the dead-wax" guide points out that big releases used several lacquers at once.

A good example of a matrix number defining a rare record: Heritage Auctions identifies the withdrawn early mono pressing of Bob Dylan's The Freewheelin' Bob Dylan, with four different songs, by the matrix numbers XLP-58717-1A and XLP-58718-1A. More examples are in rare vinyl records worth money.

Mother and stamper codes

Mother numbers and stamper codes were usually added at the plant. Some labels used letter codes for stampers, with each letter standing for a digit:

So an EMI stamper marked "G" is the first stamper and "GA" is the 13th. Low numbers suggest an early stamper, but treat them carefully: these systems were company-specific, changed over time, and sides of the same record can have different stamper codes because stampers wear at different rates.

A practical tip from the same dead-wax guide: hand-scratched matrix and mother numbers are cut into the plastic, while some stamper codes are embossed and stand slightly proud. Tilting the record under a raking light helps tell them apart.

Mastering engineer signatures

From the late 1960s onward, many cutting engineers signed their work in the runout. Two well-documented examples:

• George Peckham – the UK cutting engineer etched "A Porky Prime Cut", "Porky" or "Pecko Duck" on records he cut, often with a cryptic or humorous message. He began at Apple and later ran Porky's Mastering Services.
• Bob Ludwig – a small hand-etched "RL" marks his original cut of Led Zeppelin II. Atlantic replaced that cut with a version with reduced bass, which is why "RL" copies are collected.

US records also often carry the name of the mastering studio stamped in the dead wax; Sterling and Masterdisk are commonly seen examples. These marks help you pick the mastering a collector is looking for.

Pressing plant marks

Many major labels pressed the same record at several plants, and each plant often left its own symbol, letters or logo in the runout. Researchers have documented plant codes for labels including Capitol, Warner Bros., RCA and Mercury. These marks let you tell which plant pressed a copy that otherwise looks identical to others with the same catalogue number. Plant codes vary by label and era, so compare your marks with documented examples on Discogs rather than relying on a single generic list.

How to read and photograph the runout

The text is small, shallow and often handwritten, so:

1. Use raking light. Hold a lamp or phone torch low and to the side, and tilt the record until the characters stand out.
2. Turn the record slowly. Codes may be spread around the circle at several positions.
3. Record each side separately, exactly as written, including dashes, spaces and symbols, and note whether text is etched (handwritten) or stamped.
4. Photograph at an angle. Shooting straight down often washes out the text; a slight angle with side light gives contrast. Take a few shots at different angles.
5. Avoid reflections. Turn off overhead lights and use one directional light source.

How runouts identify the exact pressing on Discogs

On Discogs, releases with the same cover, label and catalogue number are often separated only by their runout details. Each release lists a Matrix / Runout entry per side, and for CDs also the mastering and mould SID codes. To match yours:

1. Search the catalogue number or barcode.
2. Open the master release and use "Find Your Version" to see every version.
3. Compare your runout text with the Matrix / Runout entries, side by side.
4. Pick the release where everything matches, then check its sales history.

That exact match matters for value: a pressing with one particular code can sell for several times as much as an otherwise identical copy. See how to tell a first pressing and how to price records.

CD matrix codes and IFPI SID codes

CDs carry their codes on the clear inner ring between the centre hole and the data area, sometimes called the mirror band. You'll usually find:

• A matrix number – the plant's own reference for the glass master, often including the catalogue number and a suffix.
• IFPI mastering code (L-code) – starts with "IFPI L" followed by characters. It identifies the facility that produced the master used to make the moulds.
• IFPI mould code – starts with "IFPI" with no L. It identifies the plant that replicated (pressed) the disc.

SID codes were introduced in 1994 by the IFPI and the disc manufacturing industry to help fight piracy. Philips assigns pools of numbers to manufacturers. Because one company may master and another press, the L-code and mould code on a disc don't always point to the same plant. Discs made before the system started, and some made afterwards, have no SID codes at all.

For example, one disc cited on the Kill Ugly Radio wiki carries IFPI L901 (mastering) and IFPI 2U3Q (mould). Two CDs with the same barcode but different SID codes were mastered or pressed in different places and may be listed as separate releases on Discogs. If you're sorting a stack of discs, see are CDs worth anything.

How ListMyRecords reads runouts from a photo

Typing runout text by hand is slow and easy to get wrong. In ListMyRecords you can photograph the dead wax (or a CD's inner ring), and the app reads the etched or stamped characters, including IFPI codes, and ranks the candidate releases by how closely their Discogs Matrix / Runout data matches what it read. Handwritten etchings can be hard to read, so the app shows what it read and you confirm or correct it before it's used for valuation or a listing.

Sources

• Wikipedia – Matrix number
• Wikipedia – International Federation of the Phonographic Industry (SID codes)
• pspatialaudio – Secrets from the dead-wax
• Wurzelmania – Understanding vinyl matrix information
• Kill Ugly Radio wiki – Matrix Numbers
• Wikipedia – George Peckham
• Tracking Angle – Bob Ludwig's Led Zeppelin II test pressing
• Heritage Auctions – Bob Dylan, The Freewheelin', mono LP with four deleted tracks
• Discogs – Vinyl Record Price Guide