Platinum and diamond design from the German firm, Schaffrath. The diamond floats freely in the setting, rotating on its own axis when it moves. The tip of the diamond rests loosely in a rounded cone, and from above the stone is secured by an arch.
My dad showed me how to do this & I wear mine with my wedding band. It's cool, because Do you have a quarter from 1964 or before? If you do, it is made of silver. You can turn that coin into a nice silver band using a spoon, a drill, and a metal file.