Signed not by makers mark but by characteristics. Closer set prongs on the AB chatons, I think they are called fangs. Dog Tooth prongs on the larger stones.
And BEST of ALL a reference number showing that this design has been certified # IIJJ-000596 to be an true Juliana. The Brooch in the reference number has a a slightly different colored AB stones but that is a non issue. Brilliant Cobalt Blue Oval Stones and Navettes. The one call out is a slightly bent pin. Please feel free to message me with any questions or if you would like to see more photos.