Where will is filed after letters testamentary have been granted.

If, after a will has been admitted to probate, another instrument purporting to be the will of the decedent, which has not been previously presented for probate, is filed, the court shall determine whether or not the former grant of letters should be revoked pending determination of which instrument constitutes the will of the decedent. [C66, 71, 73, 75, 77, 79, 81, §633.318 ]