An institution which has on file a power of attorney of a customer covering a deposit account or a safe-deposit agreement which has not been revoked by the customer may continue to rely on the provisions of the power of attorney in the event of the death or incompetence of the donor of the power until it receives written notice of the death or written notice of adjudication by a court of the incompetence of the customer and appointment of a guardian.
7 P.S. § 609