Elijah McCoy
Elijah McCoy was an inventor who was fascinated by steam engines
The phrase "The Real McCoy" soon caught on as a way of saying that people were getting the best equipment available.
http://www.bccns.com/elijah.htm

Elijah McCoy
His first invention was a lubricator for steam engines, U.S. 129,843, which issued on July 12, 1872. The invention allowed machines to remain in motion to be oiled...
http://www.ncalifblackengineers.org/Elijah%20McCoy.htm

Elijah McCoy
McCoy set out to create a method of automating the task of lubricating the working parts of the train. Other inventors attempted to sell their own versions of the device but most companies wanted the authentic device, requesting "the Real McCoy."
http://www.blackinventor.com/pages/elijahmccoy.html

Elijah McCoy
Frequently, if people want to make sure to get "the real thing" -- a quality product or service -- they ask for "the real McCoy." It's not certain where this phrase comes from, but many believe it started with Elijah McCoy...
http://web.mit.edu/invent/iow/mccoy.html