The Certina 263 is a manual wind, sub-second mechanical watch movement that was used during the period of 1910-. It belongs to a series of calibers including Gruen 100, 101, 620 through 623, 626, and 627. These calibers are said to be based on the FHF Robert 8.75''' movement, although specific differences between them are not well known. Reliable information regarding the Certina 263 movement is limited.