Section 171(b) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(b)By time scale. - Substantive promotions to the rank of Instructor Commander of officers, not promoted by selection against the authorised cadre of Instructor Commander, may be made, subject to their being considered fit in all respects, by time-scale on completion of 24 years' reckonable commissioned service, provided they have not attained the age of compulsory retirement. Officers so promoted shall not be reckoned against the authorised cadre of Instructor Commanders, but shall be held in a separate "non-selection" list except that an officer promoted to the acting rank of Instructor Commander before completing 24 years' service and made substantive under this clause while holding the rank of Acting Instructor Commander on completing 24 years' service shall be held against an authorised Instructor Commander's appointment.
