72For the purposes of section 336 a building is not treated as having been an industrial building—
(a)under item 5(b) or (c) or 6 of Table A in section 274 (working foreign plantations or fishing) for any tax year before 1953-54, or
(b)under item 7 of Table B in section 274 (tunnel undertakings) for any tax year before 1952-53.