This dapper chap is a Portuguese sailor ostensibly from the corvette Estefania. The Estefania was an early example of a screw corvette; previously ships had been driven by paddles, but the use of Archimedes screws as propellers was becoming more and more popular. Screw propulsion added more weight than simple sail ships but this was balanced by better performance. They were also more secure than paddle ships which had a fairly obvious point of weakness when you were in battle.
During the latter half of the 19th century, the Portuguese Navy was mostly involved with opening up trade and exploratory routes into Africa, shoring up traditional trade routes to India and Asia, and making sure Lisbon was secure from interlopers.
https://en.wikipedia.org/wiki/Steam_frigate
https://en.wikipedia.org/wiki/Portuguese_Navy#Napoleonic_Wars_and_the_early_19th_century
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