Am I seeing it correctly that the top of those jobbies stands on two legs - that there's a space between the clamping portion and the top portion? That could be significant - or not - but pouring something with a hole in it would be more work than without, which leaves me thinking the space, if it's there and not my misreading of the pictures, could be important.
They'll turn out to have something to do with leatherworking - I just know they will.