1. 12373/4 is an already existing train. SDAH-RPH intercity runs with this number.
2. The proposed TT is absolutely fake. Why would ER decide to run a SF train via BDC in the first place ? Secondly it is supposed to have a running average speed in excess of 60s upto Shri Ganganagar and run via the main line with a plethora of halts, that idea itself is laughable to me.
3. Seems like a certain member from DGR, who is gender as well as age fluid has made this TT. His...
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proposed TTs are often seen to have such ridiculous speeds.

Traces of those could not be found. Example 13287/88 South Bihar Express

The earliest records which I could find are from 1960s, when it ran between TATA-PNBE. (/blog/post/5697502)

Someone at IRFCA added...
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details to my post which I quote here

"I could locate that as early as 1941 there was a overnight 87/88 Patna Barkakana pass leaving Patna via Gaya Gomoh using Patna Gaya link. The train was all stop between Gomoh and Barkakana but Limited stops Patna to Gaya though passenger fares were charged. From Barkakana there was a passenger connection to Tata and a connection to Ranchi by NG Muri connector. During war, the train was curtailed but in 1947 or so it was restarted as Patna Tata passenger via Gaya Gomoh and Barkakana taking around 16 hours for the journey and Limited stops between Patna to Gomoh and all stop thereafter.

This pattern continued till 1962 and thereafter when the BG line to Ranchi from Muri was opened it was converted to an express and christened South Bihar Express. There was a connecting slip coaches by 87A/B from Muri till Ranchi. Now it was limited stops and was reaching Tata in 11 hours end to end. It continued like this until 1964 and while going to school in Patna we could see the 14 bogie rake parked at the Hardinge park siding having arrived at 730 or so."

So it is not possible to locate the exact history of many trains, running from centuries or so.