FREDERICK II ('The Great', King of Prussia, 1740-1786). Two letters signed ('Frederic'), Potsdam, 20 January and 1 August 1777, in French, the first to Archpriest of Rossig at Reichenbach, acknowledging a letter and expressing appreciation for his zeal and attachment to the King, ¼ page, 4to, integral blank leaf (small tears in folds); the second to Lieutenant de Zastrow of the Regiment of Anhalt-Bernburg, replying to a request to resign his commission for personal reasons, granting five months leave of absence as sufficient time to settle his affairs, ¼ page, 4to (some spotting, ink faded to a few words). -- CATHERINE II ('The Great', Tsaritsa (Empress) of Russia, 1762-1796). Letter signed ('Ekaterina') to the Kurfurst of Cologne, St. Petersburg, 12 October 1793, in Russian, announcing the marriage on 28 September of her grandson Grand Duke Aleksandr Pavlovich (later Tsar Alexander I) to Grand Duchess Elizaveta Alekseevna, née Princess Louise of Baden, requesting that he rejoice with her and expressing her warm feeling towards Cologne, 1½ pages, folio. -- CHARLES XII ('The Great', King of Sweden, 1697-1718). Letter signed ('Carolus') to Friedrich Duke of Saxe Gotha, Friedrichshalle, 29 January 1706, in German, expressing very warmly his condolences on the death of the latter's mother Christina, born Princess of Prussia, 2½ pages, folio (discoloured, tears, mainly in folds). Provenance: Viscount Mersey (circular collection stamps). (4)