First high profile East to North India train - via Dhanbad (Kalka Mail of the 1890s)
First AC Long Distance Train of India - via Dhanbad (1950s Delux Express)
First Rajdhani Train of India - via Dhanbad
First fully electrified long distance trunk route in India - via Dhanbad (HWH-GAYA-NDLS Route)
First...
more... Duronto Train of India - via Dhanbad
First Double Decker AC Train on Howrah - Dhanbad Route
First Non-Official Duronto from WB to Punjab - via Dhanbad (Durgiana Express)
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PS: IRI Members can add more interesting details :-)