These are my favourite Moonphase. On the right, Omega made these watches between 1947 and 1956. These were powered by a cal 27 DL PC AM, which was later renamed as cal 381 in 1949. On the left is the Rolex ref 8171 Moonphase powered by the bubbleback movement. The Rolex Moonphase was a failure during its launch but is considered a collectable now owing to the scarcity.