This is most likely an impact crater on the surface of what used to be a sundial. In the 80s there were about 2000+ sundials (all by the same manufacturer) that were struck by tiny meteorites. Many of the meteorites recovered were later used to develop a new kind of sundial with special meteorite repellent properties. And that is why it is very rare to find a sundial in the 90s whose surface is marred by an impact crater such as the one shown in the photo.

Unicorn Poop, (S) Navy Blue

This is the original form of a tool now made of plastic that you place in the center of a pizza in preparation for delivery. Because pizza boxes have a wide surface area, there is a risk of something crushing the box down onto the pizza which can damage the enjoyment of eating it. Delivering mushed pizzas can also hurt the pizza companies image. I believe this dates back to the latter half of the 19th century.