Often, un-resolved systems, as for example closely interacting systems of
galaxies or faint galaxies which have simply not been entered separately
in the database have both objtype=M
The simple membership to a cluster of galaxies does not imply a galaxy to carry multiple=M. M is used for member of pairs or small and close multiplets. We do not exclude that in the future this flag will be extended to code G or C respectively for members of pairs and clusters, we may also like to distinguish averred physical pairs, discordant pairs or possible pairs.