Section 134. The state purchasing agent, such officers in charge of state institutions as may be authorized by him to make purchases and officers in charge of other public institutions shall purchase brooms, mops and other supplies, other than products of prison labor, from the commission of the blind; provided, that the commission has the same for sale and that they were assembled, manufactured or otherwise produced by persons under the supervision of the commission or in industrial schools or workshops under its supervision. Said purchasing agent and officers shall, when employing persons for piano tuning, cane seating or mattress renovating, employ persons who are under the supervision of said commission or who work in any such industrial school or workshop. Any officer who wilfully refuses or neglects to comply with any requirement of this section relative to the purchase of articles and employment of persons shall be punished by a fine of not more than one hundred dollars. The term “public institutions”, as used in this section, shall include all offices, departments and institutions of the several counties, cities and towns. The commissioner may issue a release from the provisions of this section upon request of the purchasing officer of a county, city or town, when convenience or emergency requires it.