The rate of contribution of a member subject to this article shall include in addition to his normal rate, two dollars ($2) per month. Such contributions shall not become a part of a member’s accumulated contributions or be treated or administered as normal contributions and shall not be refundable to a member under any circumstances. Such contributions shall be available only for payment of survivors’ allowances under this article.

Contributions shall begin on the first of the month or the payroll period following the filing of an election to be subject to this article.