I was preparing to do a load of laundry. With 5 quarters pinched between my thumb and middle finger, I looked down and saw that one of them was not the usual nickel-copper sandwich. Damned Canadians and their quarters, I thought. Your noble deer is not accepted by my washing machine.
Upon closer examination, though, it turned out to be a 1964 Washington quarter. 1964 was the last year silver coins were minted for circulation in the United States. How exciting! I mean, I've found plenty of wheat pennies, and even a couple of silver dimes--and even once a silver Mercury dime, but never before a silver quarter. And believe me, I've looked.
The Denver mint-mark was on the reverse, under the eagle, instead of on the obverse, to the right of Washington's bust. It made a distinctly different sound as it rattled against the other quarters in my hand. A silver quarter.
Of course, there were 560,390,585 silver quarters minted in 1964 for circulation. But this is the only one I've ever found, so it was a special moment.