The proof required by section one of this act¹ may be in the form of a certificate issued by the official or body charged with administration of the death tax laws of the domiciliary state, but if such proof be not filed within the time limit set out in section one of this act, then the register of wills shall forthwith notify by mail the official or body of the domiciliary state charged with the administration of the death tax laws thereof with respect to such estate, and shall state in such notice, so far as is known to him, (a) the name, date of death, and last domicile of such decedent, (b) the name and address of each executor or administrator, (c) a summary of the values of the real estate, tangible personalty, and intangible personalty, wherever situated, belonging to such decedent at the time of his death, (d) the fact that such executor or administrator has not filed theretofore the proof required in section one of this act. Such register of wills shall attach to such notice a plain copy of the will and codicils of such decedent if he died testate, or if he died intestate, a list of his heirs and next of kin so far as is known to such register of wills. Within sixty days after mailing such notice, the official or body charged with the administration of the death tax laws of the domiciliary state may file with the orphans' court of the proper county in this Commonwealth a petition for accounting in such estate. Such official body of the domiciliary state shall, for the purpose of this act, be a party interested for the purpose of petitioning such orphans' court for such accounting, and, if such petition be filed within said period of sixty days, such orphans' court shall decree such accounting, and, upon such accounting being filed and approved, shall decree the remission to the fiduciary appointed by the domiciliary probate court of the balance of the intangible personalty after the payment of creditors and expenses of administration in this Commonwealth.