An index map shall be prepared on which shall be shown the whole area covered by the proposed tax map for each city, town and village. Such index map shall show the position of the modular unit, the section boundaries, and the number of each section map in such a manner as to serve as a key by which the section map pertaining to any location may be readily located. The index map shall be provided with a legend and a title block identifying the county, city, town or village. Space shall be provided in this block for the date of the approval by ORPTS.