Nanjing. Gan Long Iron Plate Duck, commonly known as Pipa Duck, Official Plate Duck and Male Plate Duck, is known as "North Roast Duck and South Plate Duck" and is a traditional dish in Nanjing. Pickled with salt water and dried in the sun, it can be divided into two kinds: preserved duck and spring duck. Because of its tender and close meat, it is deeply loved by the masses.