A statement in writing to the effect that wages of any amount have been paid to a person during any period, purporting to be signed by or on behalf of his employer, shall be evidence of the facts therein stated in any proceedings taken before a magistrates' court—
(a) for enforcing payment by the person to whom the wages are stated to have been paid of a sum adjudged to be paid by a summary conviction or order; ...
(b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .