Bosch puts the serial number for its dishwashers on the side of the door, not the top. Which means that 50% of the time, if the device is mounted in a corner, it's impossible to see the serial number.
Most companies use 0 and o and O in their serial numbers, as well as 1 and I. If they used nothing but letters, words in fact, there'd be no confusion. Make a list of 1000 short words, use each word twice and you have a million numbers. FISHY-LASSO, for example. Easy to remember, hard to screw up.
And there might be a reason to use really small type, but it's hard for me to understand why.
Of course, serial numbers are merely a symptom. I'm not particularly ranting about them. Design is about function. Everything we do has a job, and if it's designed properly, the job will get done well.
When we think about what might go wrong, we're more likely to design something that goes right.
[PS just found out about 3 words]