What does “MOP” mean?

MOP stands for mother of pearl, the iridescent inner layer of certain shells. It is used for watch dials, either as the full dial or as inserts, and it is popular on dress watches and many ladies' models. Because it is a natural material, each MOP dial has its own pattern and play of colour, from white and cream to darker grey and black varieties.

For dealers, MOP matters in two ways. First, it is often a factory option that changes the reference or dial code, so the papers should confirm that the watch was sold with that dial. Second, MOP is a common choice for aftermarket replacement dials, especially on popular models with added diamonds. Buyers check the printing, the finish around the markers and the paperwork to make sure the dial is original. Genuine MOP dials can also chip or crack if mishandled, so close-up photos are worth asking for.

Typical listing: “Datejust 31, white MOP dial with diamond markers, factory, 2022, full set.” The word factory is important here.