Section 39. Employees, officers and agents of any person and the person by whom they are employed may form an association for the purpose of providing annuities, pensions or endowments for employees retiring from their employment on account of age, under a system by which the participating employees contribute to the funds of the association a percentage or portion of their salaries or wages as fixed by the by-laws of the association, to be deducted by the employer and paid to the association, and the employer contributes to the funds of the association in the manner and to the extent fixed in said by-laws. The funds so provided shall be held by trustees independently of other funds of the employer, for the purchase or payment of annuities, pensions or endowments to participating employees upon their retirement from service on account of age, for the payments to the representatives or appointees of any participator dying before reaching the age of retirement, for the payment to any participator retiring from service before becoming entitled to a pension or annuity and for the payment of the expenses of the administration. An association formed under the authority of this section shall not be subject to chapter one hundred and seventy-five or to such other provisions of law as relate to insurance companies or associations, except as provided by this and the following section. Such an association may include employees, officers and agents of a group of two or more corporations engaged in the same or directly related fields of enterprise and under the same or substantially the same management.