/sys$common/syshlp/helplib.hlb DECnet-Plus, DCL Commands, SET, HOST, /MOP, Qualifiers, /VERIFICATION=hexidecimal-digits  *Conan The Librarian (sorry for the slow response - running on an old VAX)

     Specifies the service password of the remote system. A
     verification has 16 hex digits.  If less than 16 digits are
     specified, MOP will pad with zeros on the right.