And then there's the diamond itself. The 9.44ct diamond has been independently tested by the Gem Institute of America and is certified Type IIA, D Internally Flawless. Type IIA diamonds make up less than 2% of all diamonds and the designation denotes extreme chemical purity. The "D" is the highest color grade, meaning the diamond is almost entirely void of color, and Internally Flawless means exactly what you would think. The stone is emerald cut, but with a pronounced flat section in the center that allows you to clearly see the Patek caliber without distortion from facets. While this makes the stone perfect for this application, it wouldn't be the best choice for a necklace or a ring.