DM identification numbers for stars in the Bonner Durchmusterung, the Cordoba Durchmusterung, and the Cape Photographic Durchmusterung (BD, CD or CPD respectively) are given following the HD convention, i.e.
and
, the BD number is used;
and
, the CD number is used;
and
, the CPD number is used.
[]The format is 
ZZ NNNNN, with ZZ indicating the
declination zone, and NNNNN denoting a running number.
The BD, CD and CPD catalogues overlap, and in the overlapping regions their
stellar content is not identical. It may thus happen, for example, that some
stars in the zone 
only appear in the CPD catalogue. In
such a case, where the HD convention cannot be followed, the available
number is given, followed by 
in the last digit of this field. The last
digit of this field is also used for additional BD stars, i.e. stars with
suffix a or b (these stars were added to the BD Catalogue after the
original numbering was made). Such identifications do not imply that the
entry is a component of a double or multiple system.