Letters testamentary are issued is a probate matter, not a trust administration. A probate filing occurs when there is a will. Letters testamentary is a document issues by the court after a probate filing showing that a particular person or person are deemed the executor(s) of the will empowered to act upon the estate's interests.In a trust administration, its process is not a public proceeding unlike a probate. No letters testamentary are ever issues with respect to a trust by the court. In fact, in a trust adminsitration, there is no court intervention. The only time there is a court filing concerning a trust is when there is some sort of a dispute between the beneficiaries over it leading to a lawsuit.Good question.