wtf is this stuff? (found in old welding shop)

Found some weird bricks of plastic. They look like ballistic gel, but they're hard like plastic.

Some of them had a soft rubber wrapper, like they used to each be quarters of a whole with something wrapped around them.

The tops are soft/crusty.

Looks like ballistic gel, but it's a bit harder. Takes a bit of work to carve a piece off.

Smelled like motor oil, so it must burn, right? Spoiler alert, it burns.

More Burning

It takes a while to catch from a direct flame, but once it got going a little piece like this burned for a while, at least several minutes. Unfortunately, it gave off a tiny bit of black smoke like plastic would and it smells like burning plastic. As it burns, it melts and the little bits drip off and continue to burn for a long time. Eventually the whole piece just turns into a puddle and burns until it's all used up, leaving behind significantly harder black wax/tar.