(a) No cemetery corporation shall engage in the sale of monuments, not including flush bronze markers, nor shall such monuments be displayed for sale on the property of a cemetery corporation.

(b) No cemetery corporation shall authorize or permit any employee or director thereof to advertise or make known his or her relationship to such corporation while engaged in the sale of monuments outside of his or her employment by the cemetery corporation.

(c) With regard to the sale of flush granite markers, the cemetery board shall adopt reasonable rules and regulations to exempt cemetery corporations from the provisions of paragraph (a) of this section where a practice for the sale of such flush granite markers was established with the knowledge and approval of the cemetery board prior to the effective date of this section.