In this paper we consider 2-color chord O-diagrams (of order n) with one grey and (n−6) black faces under the action of the rotation group (cyclic of the order n). We have established explicit formulas for counting the number of non-isomorphic diagrams from the specified class. In addition, for natural 7<n< 30 we have also listed the exact value of the number of non-isomorphic such diagrams.


