I found a 1946 penny in my backyard when I was in high school. The original house on that lot had been built in 1946 so it was probably right from around when the original house was brand new.
When I was a kid I found an old Canadian 5 cent coin (when they were made like a dime only smaller) sitting on top of a mole hill.in the school yard. I guess I never thought it might be worth something more than buying an ice cream cone (5 cents at the time ) so I went to the bank to ask the teller if I could get a real nickel for it which she gave me and I got my ice cream cone. I don't think I even bothered looking at the date on it but if it was 1921 it could have been worth $300 - 500 dollars back then.