Notwithstanding Sections 31786, 31787, and 31787.5, upon the death, after retirement and while receiving a retirement allowance from this system, of any person who was covered under Section 31751, there shall be paid to the member’s estate, or to such beneficiary as the member shall nominate by written designation duly executed and filed with the board, the sum of two thousand dollars ($2,000) to be provided from contributions of the county or district, offset by any lump-sum death payment made under the federal Social Security Act.