N.Y. Surr. Ct. Proc. Act § 703

§ 703. Letters evidence of authority; effect of appeal\n 1. Subject to the provisions of the succeeding section, letters\ngranted by the court are conclusive evidence of the authority of the\npersons to whom they are granted until the decree granting them is\nreversed or modified upon appeal or the letters are suspended, modified\nor revoked by the court granting them.\n 2. A certificate of letters testamentary or of administration duly\nissued by the clerk of the court shall be sufficient evidence, subject\nto the provisions of subdivision one hereof, of the existence of such\nletters and the identity of the fiduciary for all purposes for six\nmonths after the date of such issuance.\n