Just for those of us who are not experts on the RN (Like me, who is most definitely not an expert.).
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Barbette and citadel ship. 1882.
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Turret and caisson ships afflicted with a case of echelonitis.
Then we have the Trafalgars:
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A turret and citadel ship. Circa 1888.
These examples could be considered evolutionary leading to this:
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Royal Sovereign class: barbette and citadel ship circa 1890.
Sources are: Wiki commons.
Well, I think that the state of steam engines at least for marine applications was still "iffy" as late as 1890. One of the things that still amazes American historians is the speed run the
USS Oregon made around the Americas in 1898. She had no major engine casualty to speak of and still managed a hefty 8-11 knot average speed from her Pacific station off San Francisco starting 19 March 1898 to join up with the North Atlantic Squadron off Santiago de Cuba, 66 days later. 14,000 nautical miles with stops for coaling and a passage through the Terra del Fuego straits through what amounted to a hurricane. This is a testimony to Union Iron Works who built her. Remember, these were American engines which are at least a decade behind British state of the art!
The General Board was convinced, because those masts on ersatz Maine are the ones as represented in OTL. it scales a bit weirder, but the masts were intended for "cruising" on sail. No really, that was the intent.
So no sails by 1884? That sounds about right as far as steam engine reliability goes. The French seem to have been more optimistic.
That is the Marceau about 1886, but laid down 1882. Source: wiki.
She is a lozenge battery turreted ironclad with the usual French tumblehome. Tough ship.