G.L. Coon was the author of A Concise History of the Klingon Empire, an important book about Klingon history as of 2293. (Star Trek VI: The Undiscovered Country)
This character was only mentioned in writing.
This author was named after Star Trek producer Gene L. Coon. He wrote the TOS episode "Errand of Mercy", which first introduced the Klingons.