Any member who has left county service and has elected to leave accumulated contributions in the retirement fund or who is deemed to have elected a deferred retirement pursuant to subdivision (b) of Section 31700 and has attained age 70 but has not yet applied for a deferred retirement allowance and who is not a reciprocal member of a retirement system established pursuant to this chapter or the Public Employees’ Retirement Law shall be notified in writing by the treasurer, or other entity authorized by the board, that the member is eligible to apply for and shall begin receiving a deferred retirement allowance by April 1 of the year following the year in which the member attains age 7012. The notification shall be made at the time the deferred member attains age 70 and shall be sent by certified mail to the member’s last known address, or to the member’s last known employer, as shown by the records of the retirement system. If the member can be located but does not make proper application for a deferred retirement allowance with retirement to be effective by April 1 of the year in which the member attains age 7012, the retirement system shall commence paying an unmodified allowance to the member. If the member cannot be located by April 1 of the year following the year in which the member attains age 7012, all of the member’s accumulated contributions and interest thereon shall be deposited in, and become a part of, the current pension reserve fund of the retirement system. The board may at any time after transfer of proceeds to the reserve fund upon receipt of proper information satisfactory to it, redeposit the proceeds to the credit of the claimant, to be administered in the manner provided under this law. This section shall not apply to a member while the member is actively employed past mandatory retirement age in a retirement system established under the provisions of this chapter or the Public Employees’ Retirement Law.