Abstract: A system and method for separating batches of mail in a mailpiece sorter. The system employs a card stock interposed between batches of mail, which card stock includes a ferromagnetic symbology disposed on a face surface of the card stock. An inductive proximity detector is employed to scan the ferromagnetic symbology and produce a ferromagnetic signature signal indicative of the ferromagnetic parameters of the symbology. The system conveys batches of mail containing the card stock past the inductive proximity detector such that the signature signals may be read and compared to predefined ferromagnetic signature signals stored in a signal processor. The processor may then determine the beginning and/or ending of a mailpiece job run for use by the mailpiece sorter.