Stuart period rose diamond  and enamel solitaire c.1680. The oval bezel contains the original, large, highly-domed foiled rose diamond, a stone of immense charm. 
The cut-down setting is undisturbed. 
Likely English in origin.
The arcades of enamel at the sides of the bezel point to the late Stuart period when this was a popular feature either in black with white dots or in sky blue enamel. 
The enamel extends down the shoulders of the plain high carat gold hoop highlighting the acanthus scrolls.
The blue enamel has been restored at some point.
Size 7.5.