Perfect Georgian simplicity, an all original high carat gold navette shaped mourning ring c.1790 enclosing a miniature navette shaped plaque with the initials LR on a bed of hair. Pretty bright-cutting on the shoulders and underside of bezel. Probably Irish.
As an obsessive for the bezel shapes of mourning rings,especially from the last two decades of the c18th, from  round, through oval, octagonal, diamond, and  oblong,I feel the navette is surely the quintessential shape of all. The navette is a symbol rooted in religious iconography, but can also be viewed as a boat that transports the soul to the afterlife.
Size 7 3/4.