SUPER rare! This Calliostoma tricolor only has one band on the front part of the last section of its last whorl while they normally have multiple. I’ve seen hundreds of their shells and this is my first time seeing this. I would imagine it was caused by a crab attack damaging the mantle, causing the shell to grow strangely. In the last two pictures you can see it compared to what a normal shell would look like. Maybe a one in ten thousand chance find?