"Sec. 2. (d) When the debtor was unable to pay an obligation which became due and demandable, or the interest which should have been paid during the said period because the assets of the creditor were under the control of the enemy and/or administered through the so-called Enemy Alien Property Custodian or other enemy instrumentality, and the debtor paid the interests to it in the belief that such payment was valid and effective payment to the creditor or because of fear that failure to comply with the demand would lead to reprisals on his person or property.

"If the debtor, however, makes a voluntary payment of the entire prewar unpaid principal obligation on or before December thirty-one, nineteen hundred and fifty-six, the interests on such principal obligation corresponding from January one, nineteen hundred and forty-six to the date of payment are likewise hereby condoned."