Question: What tiara and necklace and stomacher did Queen Louise of Denmark wear in this August Schiott portrait that is hung on a wall in the Small Drawing Room at Sandringham Estate?
According to the magazine, it's a portrait by August Schiott of "Queen Louise of Denmark, the mother of Princess Alexandra" (who of course would eventually become British Queen Alexandra).
Also, I think the portrait shown in the mirror in that room would be of Denmark's King Christian IX (Louise's husband).