This is a Pt850 0.5ct Pt platinum natural diamond necklace. The markings are: Chain: Mint Bureau mark, PT850 Top: 0.50, PT It was purchased about 15 years ago, but has been worn very little, and is in good condition. The length is approximately 21cm when laid flat with the chain fastened. (Please note that there may be some error due to amateur measurement) If you have any questions, please feel free to contact me.