A single stone diamond ring

A single stone diamond ring, the square emerald-cut diamond weighing 3.07 carats, of E colour VS1 clarity, GIA certificate 12390745, four claw-set to a scroll pierced collet, with ribbed shank and round brilliant-cut diamond-set tapered shoulders, stamped PT900 307, hallmarked London 2009, platinum 900, gross weight 4.15 grams

No. 23297M