A FRENCH GOLD DIAMOND AND BLUE GLASS 'BAGUE AU FIRMAMENT' RING, LATE 18TH CENTURY

A FRENCH GOLD DIAMOND AND BLUE GLASS 'BAGUE AU FIRMAMENT', LATE 18TH CENTURY, of octagonal form, the curved glass panel centred with a circular-cut diamond within a surround of twelve smaller diamonds, with a rose-cut diamond set surround and shoulders, with maker's lozenge RC, length 3cm, size P, fitted case