Section 100B. Every person nominated, specified or appointed under either of the two preceding sections shall be disinterested, a resident of the commonwealth and willing to act as referee. Service as referee for either party within four months prior to the date of nomination or specification for appointment, or, in case of a third referee chosen by the two referees, the date of the choice of the second referee, or, if appointed by the commissioner without specification, the date of application for appointment, shall be a disqualification for nomination, specification or appointment as aforesaid, unless with the written consent of the insured in case of a referee nominated by the company, of the company in case of a referee nominated by the insured, and of both in case of a third referee. No person shall be specified in an application to the commissioner who has been previously nominated by either party in connection with the reference proceedings to which the application relates.