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This is an archive of colorful Matrix (movie) icons. The icons themselves are Photoshop 5 documents of exactly the same 32x32 icon.
The author is unknown and Photoshop 5.5 does not reveal any metadata, but this icons set was released on May 15th, 1999.
(411.12 KiB / 420.98 KB)
Matrix Icons / compressed w/ Stuffit
Those are classic Mac OS icons pasted on Photoshop 5 documents.
Emulating this? It could probably run under: SheepShaver