Art Nouveau 18k gold diamond and plique-à-jour brooch pendant necklace

A rare Art Nouveau large scale plique-à-jour brooch of a trefoil shape in 18k yellow gold with shaded plique-à-jour enamel of soft turquoise to lilac shades in wing or leaf like motifs; the body decorated with 5 mine cut and 50 rose cut diamonds and a further diamond decorated drop suspended below with a single mine cut and rose cut diamond - It has detachable fittings and hooks and chain to convert to a pendant - Presented in its original retailers box - marked on the pin with an unidentified makers mark - total weight of brooch and chain 11.5grms - wearable length of chain 450mm - overall dimensions of brooch including drop width 51mm height 50mm - c.1890 Germany