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.