Belated Birthday wishes to 12381/82 Poorva - aka- Air-conditoined Deluxe express, which completed 62 years of service on October 2nd, 2018.
Introduced on October 2nd, 1956 from New Delhi, 81/82 Air-conditioned Deluxe express between New Delhi and Howrah was the first train in the country to operate with a A/C chair car coach and the first fully air-conditioned train. At the time of introduction, the train had seven coaches with the following coach composition -
EOG- AC 1st class - AC dining car - 3 A/C chair cars...
more...

- EOG
By February 1958, one A/C chair car was replaced with 3 third-class non-A/C coaches, making it a 9 coach train.
Initially this train operated as a bi-weekly, with 81 UP departing from Howrah at 11:55AM on Thursdays and Sundays and reaching New Delhi on the following day at 10:05 AM. In return, the 82 DN departing from New Delhi on Tuesdays and Fridays at 4:55 PM and reaching Howrah on the next day at 2:45PM. The train ran via Gaya-Mirzapur-Allahabad.
From April 1st, 1967, a weekly service was introduced via Patna numbered 103/104 (Present day 12303/04) effectively making the A/C Deluxe a tri-weekly train between Howrah and Delhi.
By 1975, the frequency of 103/104 was increased and both trains were extended to Amritsar for one run each.
The name 'Poorva' came up sometime between 1989-93 when both 12303/04 and 12381/82 were short terminated at Delhi and Paschim express was extended to Amritsar.
Attached pictures - From the 1957 NER timetable, showing the main trains on the Howrah-Delhi route. In addition to 81/82, many of the old trains can also be seen in these schedules. (Timetables courtesy of Prof.Aravind from IRFCA)