This is a fabulously scrimshawn item depicting the Paddle Steamer HMS Sphinx of 1882.
The detail is brilliant down to the reflection shown in the sea. The piece has a lovely 19th century colour to it. On reading up the history of Sphinx she spent much of her time off Africa and indeed there are pictures of coloured Natives onboard with the crew if you google her on - line. It measures 8" long x 2" diameter.