“ Each participant who has performed military or naval service before the date of separation on which the entitlement to any annuity under this chapter is based may pay to the Secretary a special contribution equal to 7 percent of the amount of the basic pay paid under section 204 of title 37 of the United States Code, to the participant for each period of military or naval service after December 1956. ”

“ The Secretary of Defense, the Secretary of Transportation, the Secretary of Commerce, or the Secretary of Health and Human Services, as appropriate, shall furnish such information to the Secretary as the Secretary may determine to be necessary for the administration of this subsection. ”

“ The annuity of-
" (A) a participant who is retired and is eligible for benefits under section 609 (a) or a participant who is retired under section 813 or is otherwise involuntarily separated from the Service, except by removal for cause on charges of misconduct or delinquency,
" (B) a participant retiring under section 808 due to a disability, and
" (C) a participant who serves 3 days or less in the month of retirement-shall commence on the day after separation from the Service or the day after pay ceases and the requirements for entitlement to annuity are met.". ”