Hi,
Pictures are always helpful for getting valuations.
If the coin isn't silver in colour, then it almost certainly has been plated as the coin itself is silver.
Plating could be gold, although another option is zinc which once heated after plating does make it “gold” in colour. Other plating options are possible too. Its a really easy experiment & great for impressing kids so it's usually done on low value coins with low value metals.
Either way, plating uses such a tiny amount of metal that it doesn't really increase the value, even if it is gold (which I doubt).
In terms of value: the silver content of the coin is about £1 which is what it'd be worth if the coin was really worn out. A fair condition circulation coin is maybe £2-3.
If the coin has been damaged (e.g. a hole punched into it to make for a necklace chain), that would lower the value.
As mentioned, the plating doesn't add any intrinsic value though it might add a small novelty value.
Any further value is determined by the jewellery itself. E.g. is it in a sterling silver ring or precious metal necklace, things like that.
If it's set into just cheap novelty metal, I'd price it as “costume jewellery” with a small premium of ~£1 or so.
If it's set in precious metal, use that as your baseline instead of the coin.
Top & bottom of it is the original coin is very common so doesn't hold any special collector value. Plating adds only novelty value. And as I say, the precious metal value is only ~£1 as it is so small & light.
Hope that's not too disappointing.
