This Hotchkiss and its accessories are lot #1116 at Morphy’s April 2019 auction:
Benjamin Hotchkiss was an American artillery designer who moved to Paris in 1867 in hopes of building a business for his improvements in artillery shells. He experienced the Franco-Prussian War in 1870, and understood the failure of the French Mitrailleuse multi-barrel volley guns. In his opinion, an effective rapid-fire weapon needed to fire explosive projectiles to have a real effect at extended range (unlike the mitrailleuse which fired simple rifle bullets). So being the inventive sort, he went ahead and designed just such a gun. His revolving cannon was sized for 1-pound (450g) 37mm explosive shells (although he would also produce armor piercing and canister ammunition). The gun looks like a Gatling gun at first glance, but its mechanical operation is quite different.
The Hotchkiss cannon would become quite popular, with major purchases by the French and American navies as well as many other nations. They would serve into World War One, including some use repurposed as antiaircraft weapons. This particular example was captured by American forces in Cuba during the Spanish-American War, most likely from San Juan Hill. It is a magnificent example of the type, and with a fantastic historical provenance to match.