Where to look
Turn the record under a light and look at the smooth, ungrooved band between the end of the last track and the label. Collectors call it the runout groove area, run-off area, matrix area or dead wax. Wikipedia's overview of matrix numbers describes the codes there as stamped, handwritten or both.
Use raking light
Hold the record so a lamp shines across the surface at a low angle; hand-etched marks catch the light.
Turn it slowly
Inscriptions can run around the circle, sometimes upside down relative to the label.
Write it down exactly
Copy every character, symbol and space for each side separately. Small differences are often the whole point.
What you may find in the runout
- The matrix number for that side, often matching a number printed on the label.
- A suffix such as a dash and a digit, frequently the cut or take number.
- Codes or logos of the pressing plant or mastering facility.
- Initials or a signature of the cutting engineer.
- Cutting or copyright dates, and sometimes earlier numbers crossed out.
All of these are described in the matrix-number overview as information intended for the factory: the main number gives the stamper a filing number and lets workers check that each side receives the right label.
Matrix number versus catalogue number
| Feature | Catalogue number | Matrix number |
|---|---|---|
| Identifies | The release as sold | One side as cut and pressed |
| Same on both sides? | Yes, usually | No, each side has its own |
| Where you see it | Spine, back cover, label in larger type | Runout area, sometimes small on the label |
| Changes when | A release is reissued or renumbered | A side is recut |
On some labels the matrix number is printed small, and occasionally even upside down, which keeps it apart from the catalogue number. When in doubt, compare: the catalogue number repeats on both labels, the matrix numbers do not.
A worked example
Here is a made-up case to show the logic. The label on side A shows 4471, and the runout reads 4471-2. The main number matches, so the label is on the right side, and the suffix suggests this side comes from the second cut. Side B may carry its own main number and a different cut, such as 4472-1.
- Match the main number in the runout with the small number on the label of the same side.
- Note the suffix after it as the likely cut or take.
- Record any plant mark, engineer initials or extra codes next to it.
- Repeat for the second side and keep both transcriptions with your collection notes.
Why cuts and stampers matter
Records are pressed from metal stampers that descend from an original cut. The glossary of the Discography of American Historical Recordings explains the chain for early discs: masters were metal-plated, from them came "mothers", and from the mothers came stampers. A stamper lasted for a limited run of pressings, after which the factory made a fresh one from the mother.
Two copies of the same album can show different numbers in the runout for a simple reason: each time a side was cut again, the new cut usually got the next suffix. Worn parts were only one reason. A faulty cut, a pressing run in another factory or country, or a later reissue could each lead to a fresh cut. Newer mastering methods of the early 1980s, Direct Metal Mastering among them, could feed far more pressings from a single cut, so wear stopped being a reason on its own.
How collectors use the runout
Runout codes help tell pressings apart: which cut you have, where it was pressed and sometimes who mastered it. Collectors compare them with discographies and with other copies to identify early cuts or known variants.
If you are buying a specific pressing, ask the seller for photos or a transcription of both runouts before you pay. Our guide on buying used vinyl covers what else to check.