Review of William Shawcross' book Counting One’s Blessings: The Selected Letters of Queen Elizabeth, the Queen Mother mentions this:
'Food in general and cake in particular loom large and by 15 she was a shrewd judge of brooches. ‘Father gave me a little horseshoe in pearls and diamonds for my birthday … It’s very pretty stones, tho’ it would have been prettier not a horseshoe.’'