Section 75. Every board, commission and department of the commonwealth, and every such county, city, town and district shall through its executive officers or board, designate one or more persons, as it may deem necessary, to act as its agent or agents in furnishing the benefits due under sections sixty-nine to seventy-five, inclusive. Such agent or agents shall be responsible for the proper carrying out of said sections under the direction and supervision of the department until his or their agency is revoked and a new agent or new agents designated. The name and address of every such agent shall be filed with the division, and, in the case of every such agent acting for any board, commission or department of the commonwealth, with the personnel administrator immediately upon his designation. This section shall not apply to counties, cities, towns and districts which have provided by insurance for the payment of compensation required by this chapter for all of their employees.