A person committing an offence under section ninety of the principal Act shall be liable on summary conviction—
where he has not previously been convicted of an offence under that section, or subsection (10) of the last foregoing section of this Act, to a fine not exceeding twenty pounds, and
where he has previously been convicted of an offence under the said section ninety or the said subsection, to imprisonment for a term not exceeding three months, or to a fine not exceeding one hundred pounds, or to both.
This section shall not apply to an offence committed before the commencement of this Act, but references in this section to a previous offence or conviction include references to an offence or conviction before the commencement of this Act under the said section ninety or an enactment reproduced in that section.
Subsection (5) of the said section ninety shall cease to have effect.