(_a_) From one classified post-office to another, upon requisition
of the Postmaster-General.
(_b_) From any classified post-office to the Post-Office
Department, and from the Post-Office Department to any classified
post-office, upon requisition of the Postmaster-General.
2. No person may be transferred as herein authorized until the
Commission shall have certified to the officer making the transfer
requisition that the person whom it is proposed to transfer has passed
an examination to test fitness for the place to which he is to be
transferred, and that such person has been at least six months next
preceding the date of the certificate in the classified service of the
Department or post-office from which the transfer is to be made.