A person who, immediately before the commencement of this Act, is, by virtue of subsection (3) of section two of the Coal Mines Act, 1911, exercising and performing, in relation to a mine of coal, stratified ironstone, shale or fireclay then exempt from the provisions of that section, the powers and duties conferred and imposed by that Act on the manager of a mine, may be manager of that mine or another mine of coal, stratified ironstone, shale or fireclay at any time at which the number of persons employed below ground in the mine does not exceed thirty and no direction is in force with respect to the mine under paragraph (b) of subsection (2) of section four of this Act or under subsection (3) of that section, notwithstanding that he does not possess the qualifications required by this Act for appointment as manager thereof.