My photobucket system shows that I posted the two photos below in October 2017.
The occasion was a visit to the London Coliseum by the King and Queen for a performance in aid of the Variety Artists Benevolent Fund.
The date was 13 December 1923
According to Hugh Roberts in The Queen's Diamonds, Queen Mary purchased the riviere of 37 stones in 1921.
Roberts also cites a Garrard Inventory dated 26 January 1920 which described the jewel as it then was as "a large brilliant riviere of 37 collets arranged to wear as a Head Ornament"
I cannot find the discussion on the RJWMB now, but I recollect that others thought that the jewel worn by Queen Mary in December 1923 was the base of the Girls of Great Britain and Ireland tiara.
I don't think that the Girls tiara would photograph as one band of light the way this jewel does.
The only description I have of Queen Mary's jewels on the evening in question is that below.