This yellow gold ring is set with five graduated sizes of precious Persian turquoise. It is Late Victorian and more specifically, the Aesthetic period. 

What makes this piece so rare is that it is an exquisite example of crafted gold work. Notice the cannetille/granulation on the shank as well as the applied filigree. The renowned Italian goldsmith Fortunate Pio Castellani was able to master ancient techniques and apply them to contemporary jewelry.