One of the things which has puzzled me since my childhood are the prison numbers of the Beagle Boys:
They all start with 176- followed by a permutation of those digits. The Wikipedia page mentions that these numbers were first applied to the third generation of Beagle Boys and not always consistently, but all comics I have read did use the 176 numbering scheme.
Is there any significance in the number 176 or the digits 1, 6, 7? Did Carl Barks chose those numbers for any particular reason? Maybe there was no specific reason, but there might be an in-universe explanation for these numbers out there.