Where a person who has been assessed as at least one per cent. disabled in respect of a prescribed disease establishes that he has abandoned any occupation as a result of the relevant disease at any time after having been employed in employed earner's employment in any occupation prescribed for that disease but before the first day in respect of which he was so assessed, then for the purpose of determining his right to, or the rate of, reduced earnings allowance under Section 59A, any occupation he has so abandoned may be treated as his regular occupation for the purposes of that section.