African-American comic book artist EMIL CECIL STONER (72) produced pencil art for the first issue of Detective Comics in 1937. Stoner went on to produce most of the artwork for the "Blue Beetle" character in the 1940s under the name "Otis" but he would often sneak in the initials "ECS" on the covers.

Source: Invisible Men: The Trailblazing Black Artists of Comic Books