Kevin Kar is an agent with the Bureau.
Whether that Bureau is in fact the Federal Bureau of Investigation is a matter that can be debated based on slightly contradictory intelligence found in this operative's adventures.
In the first recorded mission, the longest of the group, he is repeatedly called a Fed by those he deals with and he has the credentials to prove it. He works out of a DC office and heads to Florida where he works out of the Miami office of the department and comments indicate there are such field offices across the country. Even the local police treat him with respect and provide him with assistance.
After that, the FBI-ness is played down a bit and the blurb on each of these much shorter tales has them clearly listed as 'spy' cases. This 'could' lead one to believe there is some other organization called the Bureau by its members.
I vote goes to him being in the FBI, just dedicated, it seems, to dealing with cases involving spies or arms smugglers or saboteurs or the like.
Whoever he works for, Kar loves adventure and he loves stepping in front of fast moving trains - not literally, of course, but just as good as. He thinks nothing of walking into a trap because he knows it is the best way of getting answers. Naturally that means he is going to get attacked. Pounded on or shot at or something really unpleasant. He accepts the chances all the while certain that he will survive it and then wrap the case up. And he is proven right each time.
Kar is a very good looking fellow, based on how each and every woman finds plenty of reasons to want to spend time with him. Granted, more than one turns out to be a femme fatale who would like to spend quality time with him alone just before trying to end his existence. Still Kar is the man to let them have their way with him, at least up to the dispatching part.
He is also a glib talker who would have fit in better a decade or so beforehand. He is never without a pithy comment, usually said to provoke someone into action and that action is often taking a poke at him.
He would most definitely be considered a chauvinist by the way he addresses each and every female he meets, whether or not he ends up in the sack with them. "Honey", "baby", "doll". Those are the terms he uses ad nauseum. Several times over!