Where the Board of Trade have, whether before or after the passing of this Act, registered under Part II. of the [7 Edw. 7. c. 29.] Patents and Designs Act, 1907, any design forming part of the, British mercantile marine uniform, the Board of Trade shall, notwithstanding anything in section fifty-three of that Act, have a perpetual copyright in the design so long as it remains on the register.