A 19th century grisaille enamel ring

A 19th century grisaille enamel ring, the blue and white enamel oval panel centre, painted in cameo style, depicting Erato, the Muse of Lyric poetry playing the lyre, to a blue background, surrounded by a gold beaded border, all to a blue guilloché enameled band with white floral motif, all to a yellow gold mount, hallmarked Vienna 18ct gold, gross weight 5.1 grams, size X ½ , circa 1880s,

No. 30328M