Sharp EL-6190 Operation Manual page 51

Example:
If the battery was installed in November 1990, the following label would be on the
EL-6190:
Year Serial number
* When replacing the memory backup battery, make sure that the operating battery is
not exhausted.
If the operating battery is exhausted, replace it before replacing the memory backup
battery.
< Procedure >
Replace the memory backup battery using the same procedure as in "1. Replacing the
operating battery" on page 46.
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