If the veteran dies before the maturity of the loan, the amount of the unpaid principal and the unpaid interest shall be immediately due and payable. In such case, or if the veteran dies on the day the loan matures or within six months thereafter, the bank holding the note and certificate shall, upon notice of the death, present them to the Secretary, who shall pay to the bank, in full satisfaction of its claim the amount of the unpaid principal and unpaid interest, at the rate authorized by the World War Adjusted Compensation Act, as amended, accrued up to the date of the check issued to the bank; except that if, prior to the payment, the bank is notified of the death by the Secretary and fails to present the certificate and note to the Secretary within 15 days after the notice such interest shall be paid only up to the fifteenth day after such notice.