The sanctioned rates shall be the rates determined under this Part:
     Provided that if in any part of the State such rates have not been determined, a revenue court requiring the use of such rates, otherwise than for deciding abatement, enhancement or commutation of rent cases, shall in the manner prescribed work out appropriate rates after making local inspection and considering the rent generally payable by tenants of the same class for land of the same class in the vicinity, and the rates so worked out shall be deemed to be the sanctioned rates.