William Marmaduke Coffin, Jr. was born on August 14, 1887 in Covington, Kentucky.

His father, William Sr., was commissioned as a 2nd Lt. with Co. E, 5th Indiana Cavalry on August 21, 1862 and mustered out, due to being wounded twice, on May 15, 1865 as a 1st Lt.

Brother Coffin was a Past Camp Commander for the U.S. Grant Camp No. 100. At the National Encampment it was pointed out that he hadn't been a Division Commander but had served as National Counselor four times in 1913, 1914, 1915, and 1922. He would serve in that role again in 1925. He was a founder of the National Lincoln Death Day Ceremony Association.

He was a former cavalry officer serving with the 332nd Infantry during WWI. He was the Regional Manager of the U.S. Veterans Bureau.. He was a member of the Reserve Officers Association, the American Legion, Military Order of World Wars, Veterans of Foreign Wars, Forty and Eight, Disabled American Veterans, United States Military Training Camps Association, and the 332nd Infantry Association.

He graduated from the YMCA Law School and did post-graduate work at George Washington University and the University of Cincinnati. He was admitted to the bar in 1909. He continued law work almost to the end of his life. He was Regional Director of the U.S. War Risk Insurance Bureau.

Politically, he was Second Assistant United States District Attorney. (1913-1915). Through the influence of Senator A.E.B. Stephens (PCinC), he served as Secretary of the Naval Affairs Committee of the House of Representatives from 1919 until 1921.

He was a Mason, a member of the Scottish Rite and Syrian Temple Shrine, North Hyde Park Building and Loan Association, the Cincinnati Club, and the Church of the Redeemer.

He married Gladys Bowser and they had no children. After Glady's death, he married Anna Shepherd.

Brother Coffin died on December 6, 1974 in Cincinnati and is buried at Highland Cemetery, Fort Mitchell, Kentucky.