Section 19. (a) Except as permitted by paragraph (b), a municipal employee who participates as such an employee in a particular matter in which to his knowledge he, his immediate family or partner, a business organization in which he is serving as officer, director, trustee, partner or employee, or any person or organization with whom he is negotiating or has any arrangement concerning prospective employment, has a financial interest, shall be punished by a fine of not more than $10,000, or by imprisonment in the state prison for not more than 5 years, or in a jail or house of correction for not more than 2 1/2 years, or both.

(b) It shall not be a violation of this section (1) if the municipal employee first advises the official responsible for appointment to his position of the nature and circumstances of the particular matter and makes full disclosure of such financial interest, and receives in advance a written determination made by that official that the interest is not so substantial as to be deemed likely to affect the integrity of the services which the municipality may expect from the employee, or (2) if, in the case of an elected municipal official making demand bank deposits of municipal funds, said official first files, with the clerk of the city or town, a statement making full disclosure of such financial interest, or (3) if the particular matter involves a determination of general policy and the interest of the municipal employee or members of his immediate family is shared with a substantial segment of the population of the municipality.