Audemars Piguet has a long history of making some of the most beautiful and impressive perpetual calendars. The brand showed off incredible creativity with the perpetual calendar references made after the introduction of the 2120 movement in 1978. During this period from the late 1970s to the late 1980s, references like this 25618 were made in very limited production. Almost 200 different references were only made in 100 pieces, while 58 references had fewer than 40 pieces made across all metals. White gold examples were the most rare of these productions, with fewer than 200 white gold perpetual calendar watches made during this period - nearly three quarters of the production was in yellow gold. This particular example is an exceptionally rare 25618BC. According to our research, only 18 examples of this reference were produced, with 11 in yellow gold and 7 in white gold. This example, in impeccable condition, is one of only seven white gold pieces in existence, making it an exceptional addition to any serious Audemar Piguet collection.