What a rare beauty!
Made in france circa 1780, this ring at first glance looks to be a beautiful diamond and ruby cluster ring. and it is that.
However, the ring is also a work of art, formed from 5 gold bands, each holding a segment of the ring. 
Two of the bands are notched and give the shank a striped pattern when closed.
 
The rubies are set in gold and form a cruciform 
The rose cut diamonds are set in silver
The ring has french marks
 
Size 7 and cannot be sized
weighs - 6.1g
circa 1780
Excellent condition
 
The last two photos show a ring with a similar mechanism from the book 'Rings, Jewelry Of Love Power And Loyalty' six hoops each carrying a diamod letter which come together to spell the word AMITIE 
p103 , Diana Scarisbrick