If you're going to do electrical work a multimeter is essential, and with a multimeter you could work out which terminal was which.
If you're going to do electrical work a genuine understanding of how things work is essential, and if you know how lighting circuits work, and what switches do, you'd be able to work out what goes where.
There's a diagram on the back of the new switch anyway.
What there isn't on the back of the switch is a CE mark or a BS number - throw it away.
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