SECTION 11. Competitive promotional examinations

An appointing authority may make a promotional appointment on the basis of a competitive promotional examination, pursuant to the provisions of this section, which shall be open to all permanent employees of the commonwealth, or of the city, town, or district where the promotion is to be made, as the case may be, who have been employed for at least the six months next preceding the date of said examination as civil service employees in titles determined by the administrator to be eligible titles.