The term “crook of Basel” refers to a specific stylization of a charge found in the arms of Basel. In its original form, it was drawn as a bishop’s crozier [Zurich ix], but by 1413 it had assumed its present, highly stylized form [Conz.Const. ccv], to the point where it may be considered a separate charge.
Alda Mauricia bears: Purpure, a crook of Basel argent.
Hieronymus van Gent and Annetje van Leuven bear jointly as a badge: A crook of Basel Or.