A gold and micro-mosaic necklace, early 19th century, Rome

Beautiful necklace consisting of a series of medallions set in gold and centred with a micro-mosaic motif representing various famous monuments in Rome. Made of opaline glass in a rare blue-grey colour, these medallions are linked together by three finely chiselled gold chains. 
Circa 1800-1810. Excellent condition. 
Large central medallion size: 3,7 and 3,2 cm. 
Medium medallion size: 2,8 cm / 2,5 cm.