(a) If its bylaws so provide, a domestic mutual insurer may issue policies not entitled to participate in the insurer's savings and earnings, provided it is authorized to issue policies without contingent liability to assessment.
(b) Such insurer shall not issue in this State both participating and nonparticipating policies for the same class of risks, unless the right or absence of right to participate is reasonably related to the premium charge or the special character of the risks assumed.