Gatimaan Express: Raftaar meri Pehchaan - Sajid Akhtar

I was talking about the 'Punjab express', which is the precursor of the present day Doon express between Howrah and Dehradun. Earlier it was going till Lahore via the LKO-MB-ASR route, with through coaches to Dehradun. This was the only train with the name 'Punjab express'. This was a different train from the Calcutta Punjab mail.
The 'Punjab mail' is actually a very confusing name. Pre-independence, most of the trains bound to Delhi and beyond from Calcutta and Bombay were referred to as Punjab mails.
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Present day Kalka mail was a mail train from Calcutta to Delhi, with through coaches continuing on to Kalka and Peshawar by separate trains. Before 1933, it was also called 'Punjab mail'. It used to go via the main-line (Patna) between HWH-MGS. It ran with the numbers 1/2.
At the time, there was another 'Punjab mail' belonging to the Oudh and Rohilkund railway running between MGS and Peshawar with the numbers 5/6. From October 1st, 1933, the MGS-Peshawar mail was extended to Howrah via Patna, and the existing 'Punjab mail' from Howrah was re-routed via the Grand-chord (but it still had through coaches connecting to the Bombay Punjab mail at Delhi). Thus, from 1933, the 5/6 became the Calcutta Punjab mail, while the 1/2 became the Calcutta Delhi mail. With Calcutta getting a separate train to Peshawar, the 1/2 gradually started taking more coaches to Kalka and eventually became the Kalka mail. The 5/6 is the present day HWH-ASR mail.