King George VI commissioned the necklace for his elder daughter the Then Princess Elizabeth in 1950. The necklace was designed by the then Royal Jeweller, Gerrard & Co. The King used 105 loose collet diamonds that he received as Crown Heirloom from his mother Queen Mary. In total 154 Collets were marked as Crown heirloom in 1911 by Gerrard with the letter ‘C’. Queen Mery often used these diamonds to extend her existing collet necklaces.
The author of ‘The Queen’s Diamonds’ Hugh Roberts, The Former Director of the Royal Collection Trust, described the necklace as “Composed of 83 brilliants in cut-down collets, the three largest cushion-shaped, set as three graduated chains suspended from triangular clasps at either side, Pavé-set with further 22 stones, and joined by a single back chain with clasp, the individual collets with old spiral links, now fixed“.
The original piece was a bit larger than the current one. The Late Queen had Gerrard remove 10 diamonds from the piece in 1953. Queen Elizabeth II wore this necklace very often since 1950. I assume it meant much more to her given she lost her father just in 2 years after receiving the gift. The Late Queen usually paired the necklace with her Girls of Great Britain and Ireland Tiara or Queen Alexandra’s Kokoshnik Tiara.
Here is Queen Elizabeth II wearing the necklace at the 2018 Dutch state visit.