A foursome was playing a casual low-ball match at Council Fire Golf Club in Chattanooga, Tenn. They all hit their tee shots on a par 3 when this happened.
We called up a local greenkeeper to ask what cups are made out of, and how this could've happened. He said that a lot of cups are made of aluminum and are covered with plastic. Some are even made of just plastic. The best cups you can get are made out of zinc.
The part of the cup that was dented here, though, wasn't even part of a cup. It's a piece of plastic put in place to mimic white paint on the hole.
Ultimately, the shot was ruled as a hole-in-one, because the entire ball ended up below the level of the green.