In the third photo in the Instagram slideshow above (posted by Beatrice's younger sister Princess Eugenie, who took the photos), you can clearly see the ring.
Largest privately owned U.S. jewelry company Shane Co.'s VP of Merchandise Alicia Davis also said there are two smaller round diamonds on either side of the main center stone and next to the tapered diamond baguettes, which you can see if you squint at the image above. That makes five diamonds in total, NBD.
According to Beatrice's dad, Prince Andrew, Mapelli Mozzi designed the ring himself.
The ring was "designed by Edo in collaboration with the British jewellery designer Shaun Leane," the Duke of York wrote in a caption on Instagram.
“I worked with Edo closely for the past four to five months: He wanted the fusion of two elements in one ring, his love of Art Deco and Princess Beatrice’s love of Victorian style, so it’s a mix of both aesthetics,” Leane said in an interview with WWD. “There are also other elements in the ring that reflect the unity of the two of them.”