Mark020
··not the sharpest pencil in the ΩF drawerCan't determinate which reference it is (see i.e. https://universalgeneve.info/11-calendars?q=Calendar+Model-With+Moonphase) but all examples I have on record have numbers on the caseback. Caseback shoud be marked UG on the inside anyway. For instance this one: https://www.liveauctioneers.com/item/30996635_universal-geneve-full-calendar-ref-11303-around-1955