I visited the Portsmouth Historic Dockyard on Saturday and went aboard the fantastically restored HMS Warrior which was built in just 2 years between 1859 &1861. It was an ironclad sail and steamship so had to have coal delivered. The coal came in through the gun ports and was then put down chutes to the engine room below. The ship was constructed at the Thames Ironworks but I don't know if these are the original coal hole covers over the chutes or replacements when the ship was restored in Hartlepool.
The ship was obsolete within a decade and never fired a gun in anger.
It's well worth a visit. More info here: hmswarrior.org