VMS Help DECnet-Plus, DCL Commands, APPEND, Qualifiers, /BACKUP  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /BACKUP

    Qualifier type:        Input file qualifier

    Supported file types:  Local

    This qualifier selects files according to the dates of their most
    recent backup. It is relevant only with /BEFORE or /SINCE and is
    incompatible with /CREATED, /EXPIRED, and /MODIFIED.

    Default value:         Creation date