A note on the historical timeline here: Townsend was officially divorced from his first wife in November 1952. At Christmas, he told Tommy Lascelles about the relationship, and said at that time that both the Queen and the Duke of Edinburgh knew. The Queen Mother was reportedly told by Princess Margaret in February 1953. The Crown is fudging the timeline here for dramatic purposes.
But she did have another diamond ring that is now very famous: the diamond ring that Prince Charles gave to his second wife, the Duchess of Cornwall, as an engagement ring. I have no idea if the production knew about the links between the Queen Mother and that particular ring, but if this is meant to be Camilla's ring, it's a great inside-baseball reference. Camilla was divorced (with a living spouse) when she married Prince Charles -- exactly the same position that Peter Townsend is in during this episode (and that Wallis Simpson was in during the abdication crisis). The royal family's perceptions of divorce shifted radically between 1936/1953 and 2005 -- and part of that shift included the death of the Queen Mother, whose opinions about divorce, the abdication crisis, and the death of her husband were all intertwined.
A quick note about this frame: see the enormous painting in the background? This scene was filmed at Wilton House, home of the Earls of Pembroke. The painting is Van Dyck's Philip Herbert, 4th Earl of Pembroke, and his Family, which was completed by 1635. The painting depicts the wedding of an aristocratic couple whose union was doomed -- the groom died within a year of the marriage. It's also a relic from a time of incredible instability for the monarchy. By 1649, the monarchy had been abolished and the king was executed. (Be careful, Elizabeth!)
For another: Margaret never wore this necklace, which is an heirloom of the crown, in public. There is another royal with a copy of the necklace: Princess Alexandra (Margaret's first cousin) has a version without the center crown. It was given to her by her husband, Angus Ogilvy. To my knowledge, Margaret didn't have a copy. This is a necklace for the Queen, not for her sister.
What did you think of the jewels of episode six? (No spoilers here for future episodes!) Stay tuned for a look at the jewels of episode seven later this week...