Well, this ring is certainly a mysterious find! Marked with what appears to be the French eagle's head hallmark for high carat gold to the shank (tests as 18K) and a further illegible maker's mark in the french diamond-shaped style, the decorative-shouldered shank and slightly domed, shaped rear of the marquise/navette-shaped head are typically 19th century European construction - but the generously studded diamond frontage is unusual, with lots of little prongs in the silver setting between the diamonds, and the diamonds themselves hewn into unruly rose-cuts.
 
There is quite a lot of diamond here for the price, but they are variable in colour from fairly glinty and clearish-silver to darker with some yellowing, showing their age. The silver setting is quite oxidised (antique patina) giving the whole of the marquise head a moody look - we haven't attempted any cleaning.
 
It's a rather unusual thing and we're not entirely sure what to make of it - perhaps the jeweller was having an experimental phase! - but it certainly has a distinctive presence on the finger.
 
MEASUREMENTS: Head measures approx 1" to bottom. Approx ring size UK R 1/2 (US 9), or more precisely, inside diameter 19mm. 4.2g in weight.
 
CONDITION: The diamonds are of variable hue as noted and the central one is chipped, a couple of others have cracks or surface abrasions, which aren't really that noticeable given the character of the stones - please view all close-up photos and video. Any display forms/boxes are shown for photography purposes only.