Who is the real mccoy famous for in Bud Not Buddy?

In "Bud, Not Buddy" by Christopher Paul Curtis, the character referred to as "the real McCoy" is a talented musician named Herman E. Calloway. Bud believes that Calloway is his father and seeks him out as part of his journey to find his family. The phrase "the real McCoy" signifies authenticity and Excellence, highlighting Calloway's prominence in the jazz scene during the Great Depression. Ultimately, Bud's quest leads to significant revelations about his identity and heritage.