Section 28A. Five hundred dollars of any natural person in any account or accounts in a trust company, savings bank, cooperative bank, credit union, national banking association or any other banking institution doing business in the commonwealth shall be exempt from attachment by trustee process. A joint account shall be treated for the purposes of this section as if each depositor owned one half of the amount thereof. Every trustee summons served on such an institution shall describe such exemption with reference to this section. Upon service of such a summons the trustee shall answer as subject to attachment only so much money of the defendant as exceeds five hundred dollars.

No business, trust or organization shall be entitled to the exemption hereunder, and no natural person shall be entitled to more than a five hundred dollar exemption at any one time. In any action the plaintiff may apply to the court for further attachments upon proof by certified records of the trustee or trustees that the defendant has received an exemption not authorized hereunder or that the five hundred dollar exemption of the defendant has been in whole or in part exhausted or exceeded.