After scaling to the top of a large chamber, we found a few nice artifacts untouched at the top.
This bucket was one of them. Wasn't very big, probably only for candles. Had a wooden handle and was very delicate, having rusted to the ground.
It's sat here, almost certainly unseen until we found it, since the 1800's.
(Photo of Cwmorthin Slate Quarry uploaded by Penitent Miner. Please do not copy without permission).