The combination of a panel maker’s mark and the Antwerp brand made it possible to deduct that eight out of the eleven panels of the Apostle-series from Van Dyck’s workshop must have been produced as one single batch; all are branded by the assay master from the Guild of St. Luke with the same branding iron.
The Antwerp brand is the same on all eight panels and so is the monogram of the panel maker, Guilliam Gabron (active 1609 to ±1660). From Gabron’s workshop we know of two distinct punches with his monogram, one is in use from 1614-1626 and indeed used for the Apostle-series. The Antwerp brand itself is delicately crafted by the so-called ‘stempelsnijder’, the smith making punches and branding irons. The castle shows an abundance of details like windows, battlements, gates and towers. Above the castle we see the two hands with clearly defined fingers and thumbs pointing inwards. Both towers and hands were crafted in one single iron and after heating it in blazing coal it was pressed against the wood as a red-hot branding iron, leaving a clear black impression of the Antwerp coat of arms. The particular iron branding the eight panels has been found to be in use ±1618-1626.
To read more about this fascinating example of the Antwerp mass-production of panels for Van Dyck’s commission for the Apostles-series in Munich, we refer to our essay (pp. 336-339) in the ‘VAN DYCK – Gemälde von Anthonis van Dyck’ exhibition catalogue (in German) at the Alte Pinakothek, Munich, until 02.02.2020. Hirmer Verlag (ISBN: 978-3-7774-3336-3)
 Guilliam Gabron’s second punch is reappearing from 1626 through 1658. See Wadum, J., ‘The Antwerp Brand on Paintings on Panels’, in E. Hermens et al. (eds.) Looking Through Paintings. The Study of Painting Techniques and Materials in Support of Art Historical Research. Leids Kunsthistorisch Jaarboek XI (1998), pp. 179-198, De Prom/Archetype.
 Op.cit., fig. 7.