The diamond bows lower down on Queen Alexandra's skirt are, I believe, the bows which Queen Victoria left to the crown. Queen Alexandra has attached what are believed to be emerald drops and Queen Victoria's emerald earrings to them.
There is a larger diamond bow near HM's waist line.
Some believe that this bow is the same as the one later worn by Princess Margaret with a turquoise substituted for what everyone assumes must have been an emerald centre. Others dispute that it is the same bow. I personally don't know.