The department shall have supervision over, and make or cause to be made, fair and conscionable appraisements of property the transfer of which is subject to tax under this article. The appraisement, unless suspended until audit, shall be made within six months after the return has been filed and, if not so made, shall be made within an additional period as the court, upon application of any party in interest, including the personal representative, shall fix.
72 P.S. § 9137