The Battenberg course indicator is a mechanical calculating device invented by Prince Louis of Battenberg in 1892 for taking station on other vessels whose range & bearing and course & speed are known.
In 1905, Prince Louis of Battenberg, commanding the five ships of the Royal Navy's 2nd Cruiser Squadron, visited the United States, making port visits in New York City, Annapolis and Washington, D.C. Shortly after his return to England, Battenberg sent the cup to Rear Admiral Robley Evans who at the time commanded the US North Atlantic Fleet.
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Prince Louis of Battenberg, future Kaiser arrives in Bantry Bay 1892, when Kaiser he was in Bantry and was welcomed by the Prince of Wales in 1912.
Princess Victoria of Hesse and by Rhine (1863-1950), later Marchioness of Milford Haven, wife of Prince Louis of Battenberg (1854-1921) and maternal grandmother to Prince Philip, Duke of Edinburgh, might have inherited the mutation, though if so the gene remained hidden for several generations before possibly reappearing in the descendants of her eldest granddaughter, Princess Margarita of Greece and Denmark (see below).