1.  Every regular application must be supported by proper certificates of good moral character, health, and physical and mental capacity for doing the public work, the certificates to be in such form and number as the regulations of the Commission shall provide; but no certificate will be received which is inconsistent with the tenth section of the civil-service act.

2.  No one shall be examined for admission to the classified postal service if under 16 or over 35 years of age, excepting messengers, stampers, and other junior assistants, who must not be under 14 years of age, or to the classified customs service or to the classified departmental service if under 18 or over 45 years of age; but no one shall be examined for appointment to any place in the classified customs service, except that of clerk or messenger, who is under 21 years of age; but these limitations of age shall not apply to persons honorably discharged from the military or naval service of the country who are otherwise duly qualified.

  RULE XVI.

1.  Whenever any officer having the power of appointment or employment shall so request, there shall be certified to him by the Commission or the proper examining board four names for the vacancy specified, to be taken from those graded highest on the proper register of those in his branch of the service and remaining eligible, regard being had for any right of preference and to the apportionments to States and Territories; and from the said four a selection shall be made for the vacancy.  But if a person is on both a general and a special register he need not be certified for the former, except at the discretion of the Commission, until he has remained two months upon the latter.

2.  These certifications for the service at Washington shall be made in such order as to apportion, as nearly as may be practicable, the original appointments thereto among the States and Territories and the District of Columbia upon the basis of population as ascertained at the last preceding census.

  3.  In case the request for any such certification or any law or
  regulation shall call for those of either sex, persons of that sex shall
  be certified; otherwise sex shall be disregarded in such certification.

4.  Subject to the other provisions of this rule, persons eligible on any register shall be entitled to three certifications only to the same officer, but with his request in writing there may be a fourth certification of such persons to him when reached in order.  No one shall remain eligible for more than one year upon any register, except as may be provided by regulation; but these restrictions shall not extend to examinations under clause 5 of Rule VII.  No person while remaining eligible on any register shall be admitted to a new examination, and no person having failed upon any examination shall within six months be admitted