18ct = 750 = 18k = 18kt. Gold & Platinum Purity Reference Platinum = 950 = PT950 = Plat. Gemstone Type : Diamond. UK N = US 6.75 = EU 53.5 (17.12 mm). UK M = US 6.5 = EU 52 (16.71 mm). UK L = US 6 = EU 51 (16.31 mm).
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