Does anyone know of a number of pocket around 1972, which has always been "The Man …." in its title?

This series of books pocket is about a group of detectives who came from diversified funds. I think the series was created in 1940 or 1950. Each episode involved two or more of the gang as the main characters of that particular pocket book. I think the "Head" of the detectives first name was Richard. This series was published in the early mid-seventies and was designed or marketed for children over the range of 10-15 years of age. I had about 10-12 different topics for many years, for some reason a month ago the cover of an issue came to my head and I've been going crazy trying to remember the name of the series or author. The title you think I cover called "The Man From Atlantis" and had nothing to do with cheesey television starring Patrick Duffy. The cover of each issue had a hard-looking guy (Richard?) With a large cleft chin. If anyone can help me solve this would be greatly appreciated.

OK, I'm 99.9% positive are "The Avenger" books by Ron Goulart. Attached is a link that displays the works of authors, and if you scroll down you will see book covers as you describes Good luck!

Patrick Jumpen The Secret ft. Patrick Star(Doing Jumpstyle) & Spongebob