What's the chance of finding an S.O.S. shiny with a shiny charm?

Question

I have over 90% of the Alola Dex completed, and I thought I'd ask beforehand.

Answer 1

A chain length of 70 to 255 gives you a 1/1024 chance of encountering a shiny (normally 1/4096). If you have obtained the Shiny Charm, the chance becomes 1/683.

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