Computation; prior credits

The board of trustees of the pension system for each county shall include and take into consideration, when computing the period of service of each member of the pension system to determine the member's eligibility for retirement and also to determine the amount of any pension allowable to the member on such retirement, not only service as a police officer, firefighter, or bandsman in such county, but any other service under the government of the county, for which service the member would be entitled to "prior service credit" or "membership service" as defined in part II, if the member had become a member of the retirement system on January 1, 1928, as a person then in the service of the county. No additional credit for service other than as a police officer, firefighter, or bandsman, provided for by this section, shall be given to any member of the pension system unless the member shall have, on or before December 31, 1941, applied to the trustees of the pension system upon such forms and in accordance with such rules as the trustees shall prescribe, for the additional service credit. This section shall apply to persons pensioned before, as well as after, April 30, 1941, but any increase of pension resulting from the additional service credit allowed under this section shall not be retroactive as to pension payments made prior to April 30, 1941.