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Matrix Numbers, Runout Codes and Dead Wax: How to Read Them

What the dead wax on a record is and how to read its runout codes: matrix number, cut number, mother and stamper codes, plant marks and engineer initials.

Checked October 31, 2026

What is the runout, or dead wax, on a record?

The runout, also called the dead wax, run-off area or matrix area, is the smooth band without music between the last groove and the label. The codes stamped or handwritten there start with the matrix number, an identifier for that side, and often add a cut number, plant marks, the mastering engineer's initials and sometimes a message.

Collectors read the runout because it records how a particular copy was made: which lacquer, which metal parts and often which plant. Each side has its own code, so always read both. The matrix number is not the catalog number: the catalog number is printed in larger type on the label and is normally the same on both sides, while the matrix number differs from side to side, even if a version of it is printed on the label too.

How the codes get there

A record starts as a lacquer, an aluminum disc coated with lacquer, into which a cutting lathe's stylus carves the grooves. Mastering engineers mark the lacquer's runout: independent studios stamped their name into it, and engineers added their initials or a personal mark next to the stamp.

A lacquer is too soft to press records from, so it is electroplated with nickel. The first metal copy, called the metal master or father, is a negative with ridges where the grooves were. Only one metal master can be taken from a lacquer. Plating the master gives mothers, which have grooves again, and each mother is plated to make stampers, the negatives that go into the press. A stamper presses roughly 1,000 to 2,000 records before it has to be replaced.

Because each generation is a copy of the one before, anything scratched or stamped into the lacquer appears on every record pressed from it. Numbers added later identify which mother and which stamper pressed your particular copy.

The matrix number and the cut number

Album matrix numbers are often similar to the catalog number, with a side marker and a cut number added at the end. The cut number is usually the most important part: a suffix such as -3 means the third cut of that side. Masterdisk's Scott Hull gives the CBS style example AL-54321-1, where the -1 marks the first master lacquer and later lacquers got new dash numbers. A side was recut when stampers wore out or were damaged, when a cut had a technical fault, or when the program changed.

Real examples show how labels wrote it:

SHVL 804 A-2
Pink Floyd, The Dark Side of the Moon, UK Harvest, side one. SHVL 804 is the catalog number, A the side and 2 the cut. The UK first issue uses cut 2 on both sides, which is why a 1 is not always the first.
XEX 421-1N
The Beatles, Please Please Me, UK Parlophone mono PMC 1202, side one, first cut. The matching side two reads XEX 422-1N.
XZAL-9363-P-1W
The Rolling Stones, Let It Bleed, UK Decca stereo SKL 5025. On Decca, XZAL marks a stereo matrix and XARL a mono one (the mono LP reads XARL-9363), the number at the end is the lacquer and the letter after it identifies the engineer.
AL-33795-1A
Bruce Springsteen, Born to Run, US Columbia PC 33795, side one; side two is BL-33795. At Columbia, lacquers 1A to 1F were all first cuttings sent to different plants, so 1A, 1B and 1C copies are all first cuts.

Mother and stamper numbers

Many UK pressings carry extra small codes around the dead wax. Decca put the matrix at 6 o'clock, the mother number at about 9 o'clock and the stamper letter at 3 o'clock, and in general the lower the mother number, the earlier the mother used.

Decca and EMI both hid stamper numbers in a word. Decca used BUCKINGHAM: B is the first stamper taken from a mother, U the second, G the seventh, and UK the twenty-fourth. EMI used the ten letters GRAMOPHLTD, with G for 1, R for 2 and so on to D for 0, so GD is stamper 10 and GG is 11. On a Dark Side of the Moon side one reading SHVL 804 A-2 G 1, the G is EMI's code for stamper 1.

These codes help put copies of the same cut in order, but they do not date a record on their own. The Stones on Decca reference site, which documents the Decca system, says it is usually impossible to tell a first from a later pressing by matrix and stamper numbers alone, and that you need every other clue as well.

Mastering engineer marks and studio stamps

Engineer marks tell you who cut the lacquer, which collectors use to separate cuts that share a matrix number. Masterdisk's stamp, for example, was embossed by hand from a small custom die. Common marks include:

RL
Robert (Bob) Ludwig, associated first with Sterling Sound and later with Masterdisk, where he became vice president and chief engineer. His handwritten RL identifies the original hot US cut of Led Zeppelin II, whose runouts read like ST-A-691671 RL SS.
A Porky Prime Cut
George Peckham, also signed Porky, Pecko or Pecko Duck. He started in disc cutting at Apple Studios in November 1968, later set up Porky's Mastering Services, and often etched a cryptic or humorous comment into the runouts he cut. Joy Division's Unknown Pleasures (Factory FACT 10) carries A PORKY PRIME CUT on both sides.
RVG
Rudy Van Gelder, who recorded almost every Blue Note session from 1953 to 1967 and cut thousands of LP masters himself. His small RVG sits in the runout of Blue Note LPs such as John Coltrane's Blue Train, next to the matrix BN-LP-1577-A.
Wly
Wally Traugott, a lacquer-cutting engineer at Capitol Studios who cut records for the Beatles, Pink Floyd, the Beach Boys and Boston, among others. Copies with Wly on both sides are called Double Wallys. Some US Harvest copies of The Dark Side of the Moon (SMAS-11163) show Wly on side two.
MASTERDISK
The studio stamp of Masterdisk, pressed into every part cut there. Its engineers added their initials or mark next to it.

Plant codes

Pressing plants often left a mark of their own, which tells you where your copy was made. Columbia used CT or CTH for Terre Haute, Indiana, CP for Pitman, New Jersey and CS or CSM for Santa Maria, California. Blue Note's originals carry the ear, a small P for the Plastylite plant. Atlantic added a plant suffix to the number on its labels, such as MO for Monarch in California and PR for Presswell, so a Led Zeppelin II label reading ST-A-691671-MO came from Monarch.

Messages in the dead wax

Not everything in the runout is technical. Jimmy Page had Aleister Crowley's motto Do what thou wilt inscribed in the run-off groove of the original Led Zeppelin III LPs; UK copies (Atlantic 2401002) read Do what thou wilt on side one and So mote it be on side two. On Elvis Costello's This Year's Model, Peckham scratched a message saying the copy was a contest winner. Joy Division's Unknown Pleasures reads THIS IS THE WAY on one side and STEP on the other, and The Smiths' The Queen Is Dead (Rough Trade ROUGH 96) reads FEAR OF MANCHESTER and THEM WAS ROTTEN DAYS.

Because a message is scratched into one particular lacquer, it belongs to that cut, which makes it a useful identifier when you compare your copy with known pressings.

Stamped or hand etched

Note how each mark was made. Machine stamped characters look regular, like type, while hand etched ones are written freehand. The difference can matter: the UK first issue of The Dark Side of the Moon has machine stamped matrices, while the RL on Led Zeppelin II is a tiny handwritten mark.

How to read your own runout

Hold the record under a bright light and tilt it until the dead wax catches the light. Read side one, then side two, and write down every character exactly as it appears, including small marks away from the main number, whether each was stamped or etched, and roughly where it sits around the label. Then compare both sides with the pressings listed on the album's page, or search the site by runout code: the same matrix with a different engineer mark or plant code can be a different pressing.

If you would rather start from the label, the VinylLens app identifies the pressing from a photo of the center label and shows its value for every grade.

Sources

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