I planned to upload some English-language book this time. However, I stumbled upon an article about bookplates in the April'1902 issue of the Russian magazine "Искусство печати" (Printing Art,) and decided I have to share it.
Most of you probably used Excel or a similar spreadsheet software. If columns are set to be labeled by letters after Z goes AA. And then AB,... AZ, BA,... etc. But when it comes to old books, there were other ways to use letters for sorting.