I just noticed that the photo of Queen Alexandra that Beth posted in the current thread about Queen Sonja wearing the circlet shows the same dress and jewels as the watercolour. And the interesting piece with the atypical modernist design at the back has a counterpart at the front - which probably means both are part of the dress and not a pair of brooches (though one never knows with QA...). While the watercolour suggested that the baroque pearl pendant was suspended from the back of a diamond riviere, it's apparently the long chain we can see in the photo.