Laser marked articles with machine readable codes

A sheet of material that is marked with an IR pulsed laser, the sheet of material comprising an outer surface and an inner surface separated by a core, wherein there is a first layer beginning at the outer surface and extending into the core less than about 60 micron, and there is a second layer that begins where the first layer ends, is at least about 5 microns from the outer surface, and begins no greater than 60 micron from the outer surface, and wherein the first layer is substantially free of laser marking additives, and wherein the second layer comprises an IR laser marking additive at an average concentration within the range of from about 0.005% to about 2.00% by weight of the second layer.