The assertion about ID is true. All laser and inkjet printers after a certain date decades ago contain firmware that always prints microscopic dots in patterns forming unique IDs. if you scanned 1000 ballots and found the same dot patterns, you can be sure they came from one printer. For color printers, the dots are yellow and almost invisible unless you know where to look. Imaging software however can spot them quicker than the eye, and analysis can be automated to make the job easier.
The assertion about ID is true. All laser and inkjet printers after a certain date decades ago contain firmware that always prints microscopic dots in patterns forming unique IDs. if you scanned 1000 ballots and found the same dot patterns, you can be sure they came from one printer. For color printers, the dots are yellow and almost invisible unless you know where to look. Imaging software however can spot them quicker than the eye, and analysis can be automated to make the job easier.