(a) The nominating officer in any office in which a vacancy may exist shall, in form and manner to be prescribed by the Commission, request the board of examiners to certify to him the names of either males or females eligible to the vacant place.

(b) If fitness for the place to be filled is tested by competitive examination, the board of examiners shall certify the names of three males or three females, these names to be those of the eligibles who, standing higher in grade than any other three eligibles of the same sex on the register from which certification is to be made, have not been certified three times from said register:  Provided, That if upon said register there are the names of eligibles who, under section 1754 of the Revised Statutes, have claim of preference in civil appointments, the names of such eligibles shall be certified before the names of other eligibles higher in grade.  The Commission shall make regulations that will secure to each of such preference-claiming eligibles, in the order of his grade among other preference claimants, an opportunity to have his claim of preference considered and determined by the appointing officer.

(c) Each name on a register of eligibles may be certified only three times:  Provided, That when a name has been three times certified, if there are not three names on the register of higher grade, it may, upon the written request of a nominating officer to whom it has not been certified, be included in any certification made to said officer.

2.  Of the three names certified the nominating officer must select one; and if at the time of making this selection there are more vacancies than one, he may select more than one name.  Each person thus designated for appointment shall be notified, and upon reporting in person to the proper officer shall be appointed for a probational period of six months, at the end of which period, if his conduct and capacity be satisfactory to the nominating officer, he shall receive absolute appointment; but if his conduct and capacity be not satisfactory to said officer, he shall be notified that he will not receive absolute appointment, and this notification shall discharge him from the service.

3.  Every nominating officer in the classified customs service shall require the officer under whom a probationer may be serving to carefully observe and report in writing the services rendered by and the character and qualifications of such probationer.  These reports shall be preserved on file, and the Commission may prescribe the form and manner in which they shall be made.

  4.  All other vacancies, unless among the places excepted from
  examination, shall be filled by transfer or promotion.

  CUSTOMS RULE V.

  1.  Until promotion regulations have been applied to a classified customs
  district, the following promotions may be made therein at any time after
  absolute appointment: