The exceptional diamond, an internally flawless, fancy deep blue marquise brilliant-cut, has been graded by the Gemological Institute of America (GIA). The ring, dated 1923, is described in the auction catalog as “property of a lady,” though further details remain undisclosed.

The rare blue diamond is expected to fetch up to $10.3 million (HKD 80 million) at the auction, sharing the spotlight with another high-profile lot. A pair of diamond earrings, named "Oriental Sunrise," featuring two fancy vivid orange-yellow diamonds weighing 12.20 and 11.96 carats respectively, are also expected to reach a similar high estimate of $10.3 million (HKD 80 million).

Together, these two standout pieces will headline the 124-lot sale, drawing global attention to Christie’s Hong Kong this October.