List of Printers Which Do or Do Not Display Tracking Dots

Why not just use dot matrix printers?

Can be had for free from business throwing them out, ribbons are readily available, plus they can be used as generic printers (limited graphics capability, but supported both on windows and CUPS) or by writing directly to /dev/lp0

Someone from Purdue (I think) did research on being able to identify printers that used stepping motors due to unique characteristics in various models as well as individual printers.

I'm not sure if dot matrix was in the study (I want to say it was inkjet?) but the principle remains the same.

Not as precise as embedded serial numbers with watermarking, but it could get a whistle blower identified.