I used to collect coins as a kid. I still have them.
Some of the coins are from Iran prior to the revolution. So, they have the picture of the Shah of Iron on them. And some are even made of silver.
Also, when I was a kid the beer can collecting was a thing. And I also used to collect comic books. But, I do not have any of those collections any more.
Cool post. I like the collection of boarding passes. Never thought to keep those. But, it's a great idea.