That is a set of block and takle.
The ring on the side opposite the hook is replaced by the thimble in the bottom picture.
I assume the one at the top of the picture also has 2 pulleys or the thimble would be on that one.
With 2 pulleys each and a thimble on one of they it is set up to be a twofold purchase tackle. This gives a 4 to 1 mechanical advantage.