In particular, immediately south of the double star there is a very faint 14 mag star showing a purple colour. There are four other very faint 15 mag stars around the double star. It can be easily seen that the nebulosity of NGC 6188 is strong here, and extends to the north and west of the cluster. Last year I wrote a note about the bright double star in NGC 6193. In looking at this multiple star, from a suburban site, the nebulosity adjoining the cluster was no more than suspected with 7-inch aperture and no nebular filter.
Closer examination shows more components.
Curiously he doesn't mention the Dunlop companion. I have seen all six stars with the 18cm refractor at Downer, at 180x. The star cluster, being rather loose and wide, benefits from a lower power.