The one place that stands out to me as an example of the A..Z, AA..AZ, BZ...ZZ "numbering" scheme in action is in the names of columns in spreadsheets. Using letters instead of numbers then allows you to specify a row-column intersection unambiguously using terminology like "BB45".

A few other obscure uses for this kind of thing come to mind, like generating the alphabetic portions of license plates in many U.S. states, or using alphabetic characters to generate unique product IDs that are briefer than decimal or hexadecimal ones.