Stamp Error on Chip?

Since I've spend the best part of 40 years in the industrial printing industry, I'll share a potential reason for this, though I don't know in fact if this is the cause or if this is the result of mis-prints for reasons unknown.  Either could be true...

The print technology (if you want to call it that) used at the time these chips were made was known in the industry as "gravure printing".

A logo etched flat plate was coated with ink, then "squeegied off" using a sharp blade which left the "wells" of the imprint with a fast-drying UV or heat curing ink that (during the drying stage) is picked up using a silicone rubber "transfer pad", then transterred to the chip face.  After which, the chip passes under a UF cure or heat cure oven, pending the ink formulation.  This all happens quite fast.

Your photo reminds me of the effect sometimes observed of using these pads for multiple print jobs, where the ink has somewhat etched into the silicone transfer pad a bit, leaving a ghost of the previous job left behind in the chip's surface.  Most wouldn't even notice this, but under the right lighting conditions and a microscopic view, you could see it.  May be the case, not sure.