(_a_) From the classified railway mail service to any classified
post-office, and from any classified post-office to the classified
railway mail service, upon requisition of the Postmaster-General.
(_b_) From the classified railway mail service to the Post-Office
Department, and from the Post-Office Department to the classified
railway mail service, upon requisition of the Postmaster-General.
2. No person shall be transferred as herein authorized until the
Commission shall have certified to the Postmaster-General 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 railway mail service or in the classified
service of the post-office or Department from which the transfer is to
be made: _Provided_, That no employee shall be transferred to any
grade which he could not enter by original appointment by reason of any
age limitation prescribed by the civil-service rules.