PESEL is a national identification system in Poland launched in 1979. It is in fact, the only realized data system from the grand plans of the cybernetization of the socialist state. And here are some amazing visualizations from the 70s that illustrate how the system works. 1

The 1979 brochures showed how the system is supposed to work, what are its goals and consequences for citizens. The colours are amazing! Pesel unified the population records and functions to this day as the Polish equivalent of the social security number

Diagrams show the relationship between specific databases. systems or the territorial location of subsystems. I think @shannonmattern will appreciate the aesthetics of these old socialist graphs of information systems

PESEL is still in use. It always has 11 digits, identifies just one person and cannot be changed to another one (except some specific situations such as gender reassignment). https://en.wikipedia.org/wiki/PESEL