In any action or proceeding at law, where it becomes necessary to introduce such will to establish title, or for any other purpose, a copy of the will and of the record of the probate, with a certificate signed by the clerk of the superior court for the county where the will may be recorded, stating that said record and copy are full and correct, shall be admitted as competent evidence; and when a copy of a will is admitted to probate, the clerk shall thereupon issue letters testamentary. (1868-69, c. 160, s. 2; Code, s. 58; Rev., s. 330; C.S., s. 369.)