Section 16(3)(b) in Bihar Secretariat Service Rules, 2010
(b)For determination of inter-se seniority among the direct recruit Assistants appointed on the basis of examination and Assistant appointed through other sources, date of appointment / allotment order shall be treated as unit for direct recruit Assistants appointed on the basis of examination. The Assistants appointed through other sources whose date of probation is earlier from that date, shall be ranked senior to the Assistants appointed on the basis of aforesaid allotment order. The Assistants appointed through other sources, whose date of probation lies after the date of issuance of aforesaid allotment order shall be ranked junior to Assistants appointed from that allotment order.