Letter to my digital native children: the non digital library

I took my children to the library again for the 2nd time last week.  While we were scanning our returned books, I all of a sudden felt nostalgic as I wondered how I discovered the city library at their age.  Obviously there were no computers.   So how did we do it.

Each book had in the back page a plastic triangle that held a card identifying the book and a list of stamps. 

As a library member, our individual member cars were behind the counter in massive card drawers.  The were some sort of open envelope.  When we wanted to get books out, each book card got stamped by a new due date.  Stamp stamp stamp stamp...the experienced library employees stamped all cars in routine and speed.  Then the cards were gathered together in our "membership envelop", while we received our summary card with the same due date stamped. 

So at home we could see in one of the books our own membership card with the due date stamped.  There was no warning system, we had to keep an eye on that ourselves. 

I do wonder how they treated our return of books. Not quite certain how our returned books would get linked manually to the cards sitting in our individual envelope.  I've been trying to research the card system of the past online but didn't get much passed these pictures of stamped cards.  
I have no idea either how we could prolong our books, besides going to the desk, telling them our name and asking them to restamp the remaining book cars in our envelope.  I guess that's what we had to do, that we were obliged to visit the library every 3 weeks at least.  Can any of my readers remember how it worked in detail. It's weird, since I've spent so much time borrowing books as a child and yet the system details are a bit vague in my mind.  Vague but awfully nostalgic. It seemed nicer than the self-scanning nowadays 

You know what was cool : the stamps in the books gave away a hint of how often the books had been lent. Was there a good sequence of dates following or large gaps suggesting a book was less popular and not so often borrowed. Now these details are somehow hidden on some library internal KPI report. 

The search for books was also needed in big boxes of cardboxes.  I even belief you somehow could there find the due date if a book was lent...so somehow the personal stamps got linked to the book cards in the card boxes. I think...although not to certain about it anymore. who can refresh my memory?