Whoops, I guess I completely forget about this thread. Gosh, time flies!
Here are some photos for those who are interested. Using the ID on the inside of the piston (UN8459702), I determined this piston belonged to an EMD 645 diesel engine (specifically a 645E3). So this could have belonged to a GP40 or and SD40 (if I am correct?).
I found the piston listed on the National Railway Equipment website:
https://www.nre.com/parts/nre-parts-catalog?page=27I did not paint or decorate the piston. I am assuming someone at the GTW Yard/Shops in Battle Creek did that. It supposedly sat on display in the Calhoun County Tech Center for years, until it was unwanted and given to someone else. Which is who I believe I acquired it from.