Woodbridge Antiques has dated this piece to the Victorian era.
The diamonds are channel set, therefore, do not protrude.
The inside of the band is clearly hallmarked for Birmingham 1866, 18ct gold.

A lovely unisex ring!
Condition: In great antique condition (there is some very slight surface scratching to the gold commensurate with age and use and we mention only for accuracy).
Hallmarks: Birmingham 1866 18ct gold.
Measurements:
Ring size UK 0
Width across setting shoulder to shoulder: 1.2 cm approx.
Depth of band at top: 6.4 mm approx.
Depth of band at base: 3 mm approx.
Weight: 3.56 grams approx.
Woodbridge Antiques has dated this piece to the Victorian era.
Specialists in quality antique silver, fine jewellery & accessories
You can view the stock and full dealer information on the Woodbridge Antiques Profile Page