Could have fooled me! And many others.... Marked 18K, meaning 18 carat gold, with diamonds. Two rings that look like the real thing. Just, not so. Stamping anything 18K when it is not, is actually against the law. Warning, there are these kind of false stamps around, I had never seen it before!
I took them to an auction house and the expert there also assumed them to be real untill she took tests. The diamond tester I used showed as diamonds, but because the stones are set, the device picked up the metal, not the stone. And that shows up as diamonds.