Thank you The Royal Watcher and ErikS. What a wealth of information you have supplied.
When I initially read the Duchess of Teck's letter I had assumed that the brooch presented by Queen Lovisa's maternal grandparents was a new creation - obviously that was not so.
Now what we need to try to determine is who made the necklace. I presume there is no maker's mark on the jewel, otherwise I am sure that this would have been revealed long ago. Is there any evidence about which jewellers the Khedive patronised in Europe?