Fun fact, that the famous Holocaust five digit number is still used today in IBM mainframe RACFs, this is coming from the punch cards era, when the census data was tabulated in Nazi Germany with the help of Thomas Watson.

I worked at a large US bank, and we used IBM mainframes at the core, including user identity.

Every employee had a five digit number as login, no different than Holocaust prisoner number, with a prefix, indicating user account type (employee, non-employee, service acct, etc).

My IBM number was 23579