In all examinations no association shall be allowed credit in excess of its sound value for a note or security of which the principal and interest is over twelve (12) months past due; nor for any bond in excess of the real value thereof; nor for any stock of its own held more than twelve (12) months; nor for any unsecured overdrafts that may have existed for a greater period than thirty (30) days next preceding it, except that the period shall be ninety (90) days for unsecured overdrafts upon which interest is being charged if the association has a written policy authorizing such overdrafts for not more than ninety (90) days. Only such overdrafts shall be considered as secure as are advanced against products or actual existing values evidenced by warehouse receipts or bills of lading, against bills of exchange drawn in good faith against actual existing values, or against funds on deposit by the depositor whose account is overdrawn, and who has pledged those funds as security for such overdraft, and in making up the statement of the condition of such association any such item shall be charged off (but if desired a note shall be appended giving details thereof). But the discretion of the commissioner or examiner may be exercised in cases of estates in litigation or administration, and in pending suits, if the security affected thereby is ample, in the opinion of the commissioner or examiner making such examination.