It shall be lawful for any notary public or any other officer authorized to administer an oath or take an acknowledgment or proof of an instrument or make protest, who is a stockholder, director, officer or employee of a bank or other corporation, to take the acknowledgment of any party to any written instrument executed to or by such corporation, or to administer an oath to any other stockholder, director, officer, employee or agent of such corporation, or to protest for nonacceptance or nonpayment bills of exchange, drafts, checks, notes and other negotiable instruments which may be owned or held for collection by such corporation; provided it shall be unlawful for any notary public or other officer authorized to administer an oath or take an acknowledgment or proof of an instrument or make protest, to take the acknowledgment of an instrument executed by or to a bank or other corporation of which he is a stockholder, director, officer or employee, where such notary or other officer is a party to such instrument, either individually or as a representative of such corporation, or to protest any negotiable instrument owned or held for collection by such corporation, where such notary or other officer is individually a party to such instrument. No person acting in the capacity of notary public shall notarize his or her own signature. This section shall not be construed to imply that the acts herein made lawful may heretofore have been unlawful, and no instrument heretofore acknowledged or notarized before a notary public or other officer who would have been competent to act under the terms hereof shall hereafter be impugned or invalidated on the grounds that such notary public or other officer was incompetent to act.