Help with mystery mark (K 84?)

Hello - I am reposting this as I forgot to link it to a topic last time: I am wondering if anyone can help me work out what this mark might be? It looks to me like “K 84” - with a gap between the letter and number. Nothing else. When trying to do my own research all I came up with was that it could be a Russian(/Ukrainian) mark, and that K might stand for “Kiev” - but for some reason that just feels unlikely. I am attaching an image of the mark (and the necklace it is on) Thank you!

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