In the book 'Het Koninklijk Fotoalbum' (The Royal Photo Album) I found a picture of Queen Emma in 1904 with two of her ladies in waiting, where she is wearing the round star brooch (page 19). The picture is in the archives of Paleis Het Loo. The brooch is clearly distinguishable in the book - I found on the internet two other pictures where she is wearing this brooch, but less clearly visible.