I'm in the jewelry business. Generally, rings contain enough gold, and manufacturers will mark them accordingly. Merchants can't tamper with the logo. Merchants only put their own trademarks and the weight of diamonds in the ring. Since you have the logo of 18kg, it shouldn't be wrong. The gold price of 18k is 285 a gram on my side.

If you have any questions, you can find a place to recycle gold ornaments and do a test.

I hope my answer can help you.