When I planted bush delicata squash seeds last year, one of the plants produced squash of the shape you see in the photo. When I asked people on the Internet about what sort of squash were being produced, it was generally agreed that somehow patty pan squash seeds had been accidentally mixed in with the delicata seeds. However, I suspected that these were not summer squash because of their hard skins.
I was proven right today when I finally cooked the squash. These were definitely winter squash. If they had not been, they wouldn't have kept well in the cool, dark corner of the garage where they have been stored since being harvested last fall. I'm going to try planting some seeds from these squash this season and see what kind of results I get. It should be most interesting.