John Higdon wrote:

Of course they have no checksums. I'm surprised so many people did not
catch the non-literal use of the term. They do have formats and you are
tempting fate to just pull a number out of your ass.

You did say "checksum", a word that has a particular meaning, especially to
techies like us. You're just plain wrong and you don't want to admit it.
Just say you're wrong, okay?