The provisions of sections one, two, and three of this act¹ shall be liberally construed in order to insure that the state of domicile of any decedent shall receive any death taxes, together with interest and penalties thereon, due to it, and shall apply to the estate of any nonresident decedent if the laws of the state or foreign country of his domicile contain a provision of any nature, or however expressed, whereby this Commonwealth is given reasonable assurance of the collection of its death taxes, interest and penalties from the estates of decedents dying domiciled in this Commonwealth in cases where the estates of such decedents are being administered by the probate court of such other state, or if the state of domicile does not grant letters in nonresident estates until after letters have been issued by the state of domicile.