So it’s safe … until it isn’t.
As far as the garbage. Hell if I know.
According to the wiki article: "A few years later three-ring binders became the standard in the United States"
As for the number of rings: first mover advantage and network effects.
Paper is produced with three rings. Teachers buy three ring hole punches. Soon binder manufacturers target the most common standard. All other standards die off.
I have seen and used four ring binders in America. But three ring was the phrase that jumped out in my head.
The mind boggles.
3 rings: provides redundancy over 2 ring
4 ring: additional stability and redundancy
... 26 ring? At that point, you almost have more hole than paper. Is there a reason?
(4 rings for durability, 2 for convenience.)
Two-ring binders clamped at the top of the sheet.
Three-ring binders clamped at the left side of the sheet.
Four-ring binders were plastic instead of metal, and were a geared mechanical slider. One brand was the Trapper Keeper. ("Trappers" being the folders that matched them.)
At some point, the plastic four-ring binders switched to three rings to match the holes pre-punched in the loose leaf paper. But you could still get paper with 2+4 and 3+4 holes pre-punched in the left side that would fit multiple binder configurations.
Anecdotally, I've visited Chernobyl and I remember seeing somewhere a few empty cans and an empty vodka bottle. Both looked pretty recent. I've also seen the bus that's photographed. There was something inside, the thing with a cardboard cover and metal rings where you can put pages inside (It's called a "classeur" in French, but I can't find how it's called in English). Edit: as some comments pointed out, it's called a "3 ring binder" or just "binder". Thanks. It was filled with text, with different handwriting. Most of it was Eastern European, though I can't tell which languages precisely. I have a few pictures. The bus itself is near an abandonned farm with lots of farming machines left outside to rust.
I also had the chance of being here a few months before they put the second sacrophagus on the central, so I have pictures of the first.
I think the place that marked me the most was the "Monument to Those Who Saved the World" https://en.wikipedia.org/wiki/Monument_to_Those_Who_Saved_th....
One thing that I felt during my time here (two days) was how uncanny everything is. The buildings are still here, sometimes with furniture, but anything that you can easily carry has disappeared. All in all it was a great experience, I'm really glad I took the time to visit this place.
Edit: small "fun" anecdote that I like to tell: I was more irradiated during my plane trip from France to Ukraine and back than during the two days here.