If the proof required by section 54:37-5 of this title is not filed within the time therein limited, the clerk of such probate court shall forthwith notify by mail the official or body of the domiciliary state so charged with the administration of the death tax. The notice shall state:
The clerk shall attach to the notice a plain copy of the will and codicils if the decedent died testate, or, if he died intestate, a list of the heirs and next of kin so far as known to the clerk.
N.J.S. § 54:37-6