Sheffield Lab Matrix

Do not confuse with Sheffield Lab

American plating corporation incorporated Sept 17, 1979 as an outgrowth of Richard Doss, as general manager.
Please use the 'Mastered At' Label/Company credit for the time being, as instructed here.

Manufactured the metal parts used to press records: the Master/Matrix/Father discs, the Metal Mother discs and the Stamper discs.

Usually denoted by "SLM △ 00000" / "SLM △ 00000-X" etchings in the matrix/runout area or sometimes just "△ 00000" / "△ 00000-X", and optionally with a "-SH#" in (at the end of) the matrix number string (# being a number). Please use [Mastered At] when these identifiers are present and add the sequential △ 00000 number to the LCCN. (see here for an example).

Some SLM stampers have additional tally-mark etchings, featuring an "+" (plus or cross sign) with each quadrant sequentially filled in with a dot or scribble, beginning at the top left: the plus sign by itself (+) is the first stamper; the second stamper has the first top left quadrant filled; all four quadrants filled (⁜) is for the 5th stamper; a second, empty (⁜+) plus/cross stands for the 6th stamper; two filled crosses (⁜⁜) stand for the 10th stamper, etc. (example).

Please note: the cross-and-dot tally-mark system is NOT unique to plates made at Sheffield Lab Matrix. It can help to confirm an identification ONLY when known SLM markings are present. Cross-and-dots marks also appear on some Record Technology Incorporated plates, and it is possible that they were used at other plating facilities as well.