Library /sys$common/syshlp/nclhelp.hlb set, x25_access, dte_class, DNIC  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Default: Supplied by   Value: DTE address of 3 or 4 digits length
             profile

    The first part of the Network User Address (NUA). This takes
    one of two forms: Either it is in the form of the Data Network
    Identification Code (DNIC) and is specified by 4 digits, or it
    is in the form of a Data Country Code (DCC) and is specified by
    3 digits. If no profile is specified, the default is null.