It may sound turgid and dull, but this museum deals out an ace or two from an otherwise humdrum hand of traffic control and post-Liberation security milestones. The gold pistols of Sun Yatsen and 1930s gangster Huang Jinrong are worth hunting down amid the fine collection of Al Capone–style machine guns and pen-guns. Look out for the collection of hand-painted business cards once dispensed by the city’s top jìnǚ (prostitutes).