I had this exact situation at work when they shipped millions of devices with serial numbers, and didn't leave out any letter or number. Customers had so much trouble reading them accurately, I had to make a regex script that generated every possible typ0 permutation of what the customer said, and then it would list only matches from the factory database. From there, folks would try to correlate other info like dates to figure out what their real serial number probably was. It was a nightmare. Ironically several of the digits never changed, and some were just 0 1 or 2 to represent which factory made it, so there was no need for the entire character set in the first place. They seem to have been convinced we'd produce 8 quadrillion devices.
> They seem to have been convinced we'd produce 8 quadrillion devices.
While I'm not arguing that their decisions were wise nor that they shouldn't have been able to foresee and prevent the issues they caused you and your colleagues, I would add this one thought in response to the line quoted:
It's often either beneficial or at least considered beneficial to prevent business information leaking through serial numbers, the simplest example being that if you start labelling your products with 1, 2, 3.. and never deviate, then it's fairly easy to take a sample of not many serial numbers and estimate how high they go and therefore how many have been sold. Sometimes it can also be beneficial to make it harder to guess a valid serial number (eg it prevent customers from pretending to have a valid one to get a refund, or whatever).
Of course, even if you have these concerns and want to mitigate them, it doesn't prevent you from also taking steps to prevent difficulty reading the correct characters. If anything it should make them more aware of the potential issues you faced since it means someone is already actually thinking specifically about what system to use, as opposed to what likely happened in your case of someone spending 30 seconds going "we need serial numbers, using X digits means we'll never run out, job done".
> if you start labelling your products with 1, 2, 3.. and never deviate, then it's fairly easy to take a sample of not many serial numbers and estimate how high they go and therefore how many have been sold.
I bought some software many years back. The serial number had 6 or so digits in it. At one point, I contacted the developer for some other purpose, and pointed out that I had made my purchase as soon as I heard about the product. He told me I was the first customer, and that he had decided to make up long serial numbers to avoid this counting problem.
It also works great as a checksum. See IBAN numbers for a great example - they are all multiples of 97 plus 1 which makes accidental typos much less possible.
