Does anyone know what this is?

I found it today. It's flattish, shaped roughly like an equilateral triangle with 3" sides, and very heavy. It feels like iron. It's covered on both sides with a beautiful iridescent enamel with thumb-size depressions in the three corners and semicircular cut-outs in the sides. There's a hole in the centre with a decorative surround.

Is it a paperweight or something to fidget with, like those spinners that were so popular last year?
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