I saw one blade that looked like that, I caused it...
During my first job on a Christmas tree farm, the owner had me cutting his lawn with a snapper mower. He was known to buy cheap parts, I was mowing under the Walnut tree, hit a Walnut, and put a perfect 90 degree ear on one side of the blade. By the time I got everything stopped and shut down, it looked like a helicopter crashed in the yard, it got worse.
Since the snapper was out of commission, he set me up on the Kubota and away I went. It was the biggest tractor I had run to date at the age of 14. Not thinking about the headache rack on it, I managed to efficiently remove all of his wife's clothes lines. I was never tasked with mowing the yard again.