(1) Where:
(a) a person to whom pension is payable under section 52 is reclassified under section 53 during a prescribed half - year;
(b) the person became entitled at the commencement of that half - year to an increase under this Part in the rate at which the pension was payable to him immediately before the commencement of that half - year;
the rate at which the pension is payable to him on and after the date from which the reclassification has effect is the rate at which the pension would have been payable to him at the commencement of that half - year if his classification, on and after the date on which he became entitled to the pension, had been in accordance with the reclassification.
(3) Where:
(a) at the commencement of a prescribed half - year a person entitled to invalidity benefit was classified as Class C under subsection 51(2) but was not entitled to pension under section 52; and
(b) during the prescribed half - year the person is reclassified as Class A or Class B;
the rate at which a pension is payable to the person on or after the day from which the reclassification has effect is the rate at which the pension would be payable to the person on that day if, at all times during the period during which the person was classified as Class C, the person had been classified as Class A or Class B (as the case may be).