From the famed Maison Boivin, this is a rare and extra-ordinary ring, and very few were made. Boivin made a similar bracelet for the Duchess of Windsor, which is on p 71 in the Boivin book. There is a full page picture of a similar ring on p 327, but the emeralds are not as good as ours. It is likely that only two were made. The emerald beads are set on a gold wire circle, and move with the wearer. The band is beautifully detailed. It dates from 1947.
The ring is an American size 7. It can be made a bit smaller by adding a clip to the inside, but it cannot be made larger.