The present two plates are variations on a service originally created as a gift from King George III and Queen Charlotte to her brother Duke Adolphus Frederick IV of Mecklenburg-Strelitz.
See F. Severne MacKenna, Chelsea Porcelain, The Gold Anchor Wares, London, 1952, pp. 16, 66 and plate 9, no. 16 for the illustration of a plate with fanciful birds in the center, at that time with Winifred Williams. MacKenna mentions that a service of this decoration sold at Christie's in March 1764, described in the auction catalogue as "...the same as the Royal Pattern that was sold for 1150 pounds. This service is declared to be the last that will be made."