Alright, so basically in 1944, the main train running from Sealdah to Tinsukia was the Assam Mail. This bad boy passed through what's now Bangladesh. Back then, there wasn't another train heading to Tinsukia, so there was no Tinsukia Mail at that time. Some folks just called the Assam Mail the Tinsukia Mail though.
Nope, there wasn't any train called the Assam Mail from Delhi until 1959.
The jam in North India was the meter gauge railway connecting Lucknow Jn to Guwahati (after Saraighat bridge came up in 1962). There was the Awadh Tirhut Mail at 1 Up and 2 Down, also known as the AT Mail, with its slick blue carriages and a snazzy yellow YDM4 engine. Then there was the Guwahati Lucknow Express, known as GL by the peeps.
Huge shoutout for all the dope blog posts!

Main 1944 ka timetable dekh raha tha aur mujhe 3 up 4 dn Sealdah Tinsukia Assam Mail mila. Iska route aaj ke Bangladesh se hota tha. Mujhe Tinsukia jaane wali koi aur train nahin dikhi. Toh, tab koi Tunsukia Mail nahin thi. Assam Mail ko kuchh log Tinsukia Mail bhi bula sakte the.

Delhi se Assam Mail nahin thi 1959 tak.

Uttari Bharat ka route meter gauge line tha Lucknow Jn se Guwahati tak (Saraighat bridge 1962 mein khula). 1 Up 2 DN Awadh Tirhut Mail jo ki AT Mail ke naam se jaani jati thi aur jisme sundar blue colored coaches aur ek yellow YDM4 loco tha. Dusri train Guwahati Lucknow Express thi, jo ki GL ke naam se jaani jati thi.

Thank you for your blog posts.