[HerrKaiser]

Building on Kyrie’s last answer, the nomenclature sometimes also classifies my commercial as a “1923” commercial since it has a 5 digit SN (80395), despite it having likely been made in 1920-21 or so. Somewhere in the 85000 range they switched to the “alphabet” system (or 1920) commercials such as yours. Try making sense of that...
Me personally, I call the ones like mine “1920 commercials” and the ones like yours “alphabet” commercials for clarity.