Bart Adams, the Hunter, is an agent with American Intelligence.
Exactly what agency he works for is never specified but since his activities take him all over Europe, its reach is extensive and its primary concern is fighting the never-ending Cold War against communists. While he could be working for the CIA in those fairly early days of that organization, he could also be attached to Military Intelligence as it was said to be quite active in that first decade after the Second World War.
Adams is a man who enjoys assuming disguises and he is quite good at it, allowing him to take the role of numerous people and professions and to blend in beautifully in all manner of situations. We could just as likely see him in a top hat and tails, dressed impeccably for a night at the opera, or see him in worn-out overalls and ascot cap moving with slow plodding steps after a long day at the factory or the wharfs.
Since he dons these various personas all over the Eastern European area on many occasions, it is safe to assume that he is able to speak a good number of languages natively as he does not just look the part but also acts and talks as such.
Adams is almost certainly single as he never shows any indication of someone waiting back home. He is in his early-to-mid 30s of average height and weight and looks. This "every-man" appearance certainly aids quite a bit in his disguises as there is nothing either good or bad that stands out about him. He is able to achieve frequently the goal of many undercover operatives - he is prosaic enough to be unnoticeable.
As mentioned above, Adams roams about the communist nations of the Iron Curtain with great apparent ease. He will visit Romania, Albania, Hungary at least once, Bulgaria and Czechoslovakia twice, and Germany and Poland three times. He will even find his way into Mother Russia at least once. He will also operate in England, France, Austria, Denmark, and Greece as well as a trip or two back to the States in the numerous recorded adventures we have of his.
In all these places and times, the Hunter hunts alone. We never see him with any noticeable backup but it is quite apparent by the number of contacts that he has all over Europe that he has been a very busy operative and he is not at all adverse to calling upon them for a little help now and then.