The Watch: Blancpain relaunched in 1983 on the strength of a complete calendar with moon phase, and the layout it settled on then has not changed since. Day and month sit in twin windows below 12. The date is read off a serpentine hand with a crescent tip that sweeps the outer chapter. The moon phase occupies an oversized aperture at 6.
The Bathyscaphe entered the Fifty Fathoms collection in 1956 as the smaller, more wearable diver. This reference puts the Villeret calendar into that case at 43mm in steel, water resistant to 300 meters, with a graduated bezel and a sunburst meteor grey dial. Because who doesn't find themselves 300m below the surface and wondering about the day, date, month, and phase of the moon?
Inside is the cal. 6654.P.4, automatic, 72 hours of reserve, visible through the sapphire caseback.
