VGFacts

http://fallout.wikia.com/wiki/File:Drawi...hanist.png
That is a poster you can find at the end of Automatron. It is signed DP.

http://fallout.wikia.com/wiki/Derek_Pacion

This is Derek Pacion. He is a kid in the town of Canterbury Commons, the home of Fallout 3's Superhuman Gambit quest, where the mechanist originates from.

http://fallout.wikia.com/wiki/The_Superhuman_Gambit

http://fallout.wikia.com/wiki/Mechanist

If you've gotten far enough into Automatron, you will know

Seeing as there is not an immediately obvious correlation between the Fallout 3 mechanist and the Fallout 4 mechanist, and the fact that it was revealed to be a radio show character in 4, I figure its worth noting the reference to Derek Pacion. He did create the drawing which inspires Ms. Cruz to become The Mechanist, and it isn't explicitly stated.