Found this in a bric-a-brac store and no one seemed to know what it was used for so here is an explanation.
“Scientists and engineers developed several commercially important types of battery. “Wet cells” were open containers that held liquid electrolyte and metallic electrodes. When the electrodes were completely consumed, the wet cell was renewed by replacing the electrodes and electrolyte. Open containers are unsuitable for mobile or portable use. Wet cells were used commercially in the telegraph and telephone systems. Early electric cars used semi-sealed wet cells.”
I use it for string and brushes at my small sink so I can see at a glance what’s inside. Mine has a lid too which I am grateful for.