It is no bake clay (even after sitting for over a decade it is still soft and oily, which is why it is covered in dust), I found that out the hard way. The first version melted in the oven.

What's it made out of?

I was reading that pure clay can be extracted from most types of soils, and isn't an unusual amount of work to do so. Was thinking about baking some objects one of these days...

Ack! Pfft!

I made it somewhere between 15 and 20 years ago, so I do not remember the exact brand of the clay. It is not actually clay, it is some kind of polymer. It is supposed to be air dry, but I never fully hardened.

covered in dust

I think that just makes it look more like Bill.

I've used an air dry clay,that seemed to be an organic clay, to make Rosaries and they actually turned out well. The beads took a couple weeks to dry fully and then I took a paper clip and burnished them with the edge until they took on a shine. I don't remember the brand. It was sold in small blocks at a US chain of hobby stores called Hobby Lobby.

Oh, absolutely. Constantly oily and dusty? Bill!!

Yikes, Hobby Lobby. But that's interesting about burnishing with a paper clip. I didn't even realise one could do that. :o

I do have some Sculpey polymer clay. I've found that it can crack over time, though, so might be suited to more temporary projects.