In his letter dated 18 May 1818 referred the Dutch minister of navy to an royal decision dated 9 May 1818 no. 74 ordering that midshipmen no longer were to wear epaulets but instead since 1 July a gold distinguishing sign at the front of the collar in the shape of a buttonhole as shown on the photograph.
Source
Archive Marine Etablissement Vlissingen , Netherlands (Zeeuws Archief, Middelburg) 95.16
