Consider:
Victorian England 1837 - 1901
American Old West 1803 - 1912
Meiji Restoration 1868 - 1912
French privateering in the Gulf of Mexico ended circa 1830
Conclusion: A adventuring party consisting of a Victorian gentleman theif, an Old West gunslinger, a disgraced former samurai, and an elderly French pirate is actually 100% historically plausible.
