If a municipal employee or officer, who was not previously retired or pensioned, who has paid into the fund the full amount of his annual assessments or contributions and who shall have served in the municipal employ for five years, shall die from causes other than injuries or illness received or incurred in the performance of his duties, twenty per cent of the pension which would have been paid if he had served in the village for twenty-five years shall be paid to the surviving widow, husband, minor children or dependent parents, as the case may be. For each additional year of such service thereafter the proportionate amount of the pension to be so paid shall be increased to the extent of four per cent over and above such twenty per cent per annum for each additional year of service up to and including twenty-five years.