Yorke Norroy is an agent of the State Department.
In the time in which he worked, namely the turn of the 20th century, he was referred to as a "diplomatic agent" employed by the Department of State. The term spy was not used, you see, in polite company for it gave a rather negative cast to the profession and Norroy was above all that. By this I mean he was above giving a bad impression. He most certainly was not above doing whatever it took to get the job done, negative or otherwise. He just would rather not look like he was anything but a polite member of the gentry.
In the opening pages of the first recorded adventure, very astute and important descriptions of Norroy are given which sum up very well the type of man that he presented as well as the style of writing all the adventures would employ:
"Seen from [a] distance, there was nothing particularly striking about him. Looking at him more closely, such an impression would be cast aside. There was something impressive in the way he held himself; and his indefinitely colored eyes had in them a certain commanding, almost supercilious look which stamped him as a man who did things.
"His hair was cut very close to the scalp, showing a pair of small, very perked-up ears, which seemed to have almost human alertness in the way they apparently stood to attention. He was of medium height, neither tall nor short, although his excessive slenderness inclined to the first impression. His hands and feet were very small—almost womanish, in fact. His clothes were just a little too much the mode of the day, and one indefinably regretted that a man of his intelligence should spend the thought necessary for such ultra-fashionable attire. They had evidently been cut not a week before, for they embodied a new wrinkle in evening clothes which had originated at the period.
"The objection which most people found in Norroy was that he was just a bit too sphinxlike in his facial expression, and that he had mastered the art of saying less in more words, when he chose, than any man in the circles in which he moved. It seemed to be Norroy's principal aim in life to persuade people that he was simply an idle butterfly of fashion, without any more brains than the modicum usually portioned out to men who make the pursuit of the fashions and the ways of the ultra-mundane their sole object of living.
"When in Washington, New York, London, Paris, or any other city where the society folk of America sojourned, he was of them, one of them, and nothing more. Yet everyone knew that much of Norroy's time was spent in other places; where, he would not tell, but every now and then he disappeared, and questions were unavailing, for none knew or could learn of his whereabouts."
Norroy's age is not specifically mentioned but he is likely in his late 20s going by the history that is alluded to and the fact that he fits in so well with those of that age in his adventures. Furthermore, his boss, the Secretary of State, treats him, while very respectfully, as someone quite a bit younger. There is no disrepect, though, in the boss's attitude for he has already learned before the first book how well Norroy can perform and how determined Norroy is in getting results.
For his own part, Norroy admits to himself that he does much of what he does not only because it is important to the country he loves but because he really enjoys his work. He is obviously quite gifted at it and while he knows there is always a chance of failure, the concept of his actually letting it happen never really takes hold in his head. He just will not allow it.
Norroy is not officially a part of the government bureaucracy. He is an independent agent and he can and apparently does do work for others but he is largely at the beckon of the Secretary and drops everything when so called. His patriotism notwithstanding, though, Norroy is not above concerns of money. Though he gives the appearance of a wealthy "dandy" he decidedly worries about getting paid and pays attention to things like expenses. It obviously takes a lot of money to look like one does not need to worry about money.