There are a few quality and trustworthy gemological laboratories, and GSI is one of them. All the diamonds are graded with the usage of modern and quality equipment, which significantly reduces the chance of human mistake. It offers different grading reports, laser inscribing, and other services. Also, you can find more about gsi rating on their official site.
It's important to grade your precious stones because there are many fake ones, and spending money on them isn't pleasant.