For me am not sure whether it was 2640 or 6008.. but remember some journeys with 6023
6023 the most moment i remember was arriving close to Twillight to JTJ.. The Eloco used to be detached and it used to be sent through the next line towards MAS side to take the returning train.. Dloco used to be attached for 6023 to proceed the journey. And while we used to be received on PF-1 of SBC , another dloco will be on PF-2 with the 6525 Nagercoil Express waiting for departure