Subject to the time limits and other conditions published by OPM in its operating manuals, the following persons are entitled to file applications for open competitive examinations after the closing date for receipt of applications when there is an existing register or a register about to be established:

(a) A person who could not file an application during the filing period, or appear for an assembled examination, because of military service, or hospitalization continuing for 1 year or less following discharge from military service;

(b) An employee of the Federal Government who, as a member of a reserve unit of the military service, could not file an application during the filing period, or appear for an assembled examination, because of active duty beyond 15 days with the military service even though the duty is designated for training purposes; and

(c) A United States citizen who could not file an application during the filing period, or appear for an assembled examination, because of overseas service with a Federal agency or with an international organization in which the United States Government participates.