Every guardian shall invest the surplus funds of his or her ward's estate in such securities or property as authorized under the laws of this state but only upon prior order of the court; except that the funds may be invested, without prior court authorization, in direct unconditional interest-bearing obligations of this state or of the United States and in obligations the interest and principal of which are unconditionally guaranteed by the United States. A signed duplicate or certified copy of the petition for authority to invest shall be furnished the proper office of the veterans administration, and notice of hearing thereon shall be given said office as provided in the case of hearing on a guardian's account.