Permanent identifiers should not carry data. This is like the cardinal sin of data management. You always run into situations where the thing you thought, "surely this never changes, so it's safe to squeeze into the ID to save a lookup". Then people suddenly find out they have a new gender identity, and they need a last final digit in their ID numbers too.

Even if nothing changes, you can run into trouble. Norwegian PNs have your birth date (in DDMMYY format) as the first six digits. Surely that doesn't change, right? Well, wrong, since although the date doesn't change, your knowledge of it might. Immigrants who didn't know their exact date of birth got assigned 1. Jan by default... And then people with actual birthdays on 1 Jan got told, "sorry, you can't have that as birth date, we've run out of numbers in that series!"

Librarians in the analog age can be forgiven for cramming data into their identifiers, to save a lookup. When the lookup is in a physical card catalog, that's somewhat understandable (although you bet they could run into trouble over it too). But when you have a powerful database at your fingertips, use it! Don't make decisions you will regret just to shave off a couple of milliseconds!