Frontier Mail had the numbers 3/4 right through from Bombay to Peshawar. 57/58 was known as GIP Bombay Express, and also went to Peshawar. 5/6 Punjab (Calcutta) Mail ran from Howrah to Lahore. 17/18 was a Link Express between Lahore and Howrah, with coaches attached to the Doon Express at Laksar. You can see the originally Lahori Passenger here from Lahore to Dehra Dun (today's ASR - DDN Express). 67/ 68 Coaching Express seems to be forerunner of the ASR - Delhi Janata Express, which has since vanished. The mainline from Lahore to Delhi was via Saharanpur, with only 57/58 taking the shorter route via Panipat.