I don’t see any doubling on 1976 quarters, just circulation wear and damage. The 1965 you posted has environmental damage. Probably a metal detector find.
Quick question @Marites Foertsch, are you looking to strike it rich on an error coin, or do you really want to learn about coins as a collector? From your many photos posted and questions, I get the feeling it is the first.
You would be much better off if you want to look for error coins to first learn all you can about them. Right now it looks like you can't tell the difference between damaged coins from circulation wear and tear and a real mint error . I hope this helps you and good luck.
I’m buying and collecting sir. But I do really wanna learn about error and everything. Thank you and have a good one. No more posting for a while