In Jeff Liebermann writes:

[snip]

Machine Identification Code
https://en.wikipedia.org/wiki/Machine_Identification_Code

I recently inherited from a customer an HP LaserJet Pro m477fnw color
laser printer:
https://www.amazon.com/HP-Color-LaserJet-M477fnw-Renewed/dp/B01N5XP9TL/
Quite good, but this particular model doesn't do double sided
printing. When I picked up the printer, the yellow toner level was
well below the other colors. The dots are visible with a microscope
and UV illumination.

Grumble...

Periodically, the great folk (overworked, understaffed...)
at the EFF do things like:

https://www.eff.org/pages/list-print...-tracking-dots


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Knowledge may be power, but communications is the key

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