(1) Where, for the purpose of computing the payments to be made under section 66 of the Currency Act by an Associated Bank which was, at the passing of that Act, a bank of issue, it is necessary to have regard to the total amount, as ascertained by the Commission, of the notes of such Associated Bank outstanding (including notes in the tills or vaults of such Associated Bank) immediately before the appointed day mentioned in section 60 of the Currency Act, such Associated Bank may, for the said purpose, from time to time write off, with the sanction of the Minister, from the said total amount as so ascertained an amount not exceeding the amount of so many of the said notes of such Associated Bank still outstanding at the time of such writing off as are estimated by such Associated Bank to be unlikely ever to be presented to such Associated Bank for payment.