Phil Scott is an agent of the U.S. government.
The agency for which he works is unknown (to me) but his designation in that organization is Secret Agent xx96. What that stands for, especially the x's is also known.
What little I have gleaned is that Scott was a professor whose specialty had to be sex or sexuality or psychology because as the series begins, accord to Erin E. MacDonald's Ed McBain/Evan Hunter: A Literary Companion, he is "professor recruited to become a spy and sent to convince a beatiful Russian agent to defect."
No other information is available as I have not found the books cheap enough to buy.
In the heyday of sex novels hitting main stream, Greenleaf Publishing was a giant in the industry and besides producing an incredible number of books, it was able to grab many up-and-coming authors and give them a chance to either perfect their craft or at least earn a few bucks.
In the case of the Phil Scott books, written by noted author Evan Hunter, known even better by one of his many other pennames of Ed McBain (87th Precinct), this had to have been a coup. Mr. Hunter was already an established writer. He certainly did not need to learn to sharpen his prose in 1966 when he started producing for Greenleaf under the penname of Dean Hudson. But produce he did, dozens of books of all sorts having sex as the one common demoninator.
In 1966, "Dean Hudson" came up with his own spy to join the many, many spies in fiction out at that time. Since the publisher was worried about getting nabbed by the government, he changed imprints a lot, which is probably one reason the series is so little known - that and the books would not have been found in drug stores and supermarkets like regular books could be then.