SYMBiFACE II uses a Dallas DS12887A RTC chip. [https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/real-time-clock-board/msg249380/#msg249380 Source]
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According to This chip is a modernized version of the datasheetMC146818, this the original RTC chip used in the IBM PC/AT. It includes a built-in battery and crystal, making it more reliable. It has 14 bytes of registers and 114 bytes of battery-backed static RAM. It's ram inside the device. Century register doesn't exist on this particular model.
It is a [[PC compatible RTC chip]] and is programmed in the same way.