Ship's Deck Filler Cap
No, this is not a giant's bath plug hole! It is, however, a filler cap and mount, made from solid brass with screw fitted removable cover which is attached with a safety chain to avoid loss whilst at sea. This would probably have been flush fitted to the ship's deck to give access to either diesel or water tanks. The item's diameter is 7.5" (19cm) and is 3.5" (8cm) deep. Great for a classic boat restoration project or possibly shore based applications!