James Dillingham Young is twenty-two years old. He is a hard worker, quiet by nature, and very devoted to his wife, Della. He is employed at a job of some sort in a large city - while no specific details are given, it might be some sort of office work where he would have had reason to wear his family heirloom pocket watch, particularly if it was securely held in place with "a platinum fob chain...properly proclaiming its value by substance alone". Jim's income has been reduced, however, from $30.00 per week down to $20.00 per week, an amount that has required Jim to find a creative new way of raising enough money to purchase a Christmas present that is an appropriate expression of his love for Della.
The middle name Dillingham plus the fact that Jim inherited his gold watch from his father who had inherited it from Jim's maternal grandfather suggest that Jim comes from a social class superior to that to which he and Della now belong. The name Dillingham in itself does not necessarily mean that Jim comes from a higher class, but the fact that O. Henry puts it in the story and emphasizes it shows the author intended to imply something--if only to explain how a man in Jim's position could come to own an expensive gold watch. Jim values his watch because it is a reminder of his ancestry. That is why he is always taking it out and looking at it. The fact that he is always pulling his watch out of his pocket suggests that there is a mathematical probability of his dropping it sooner or later. That was why men had watch fobs for pocket watches, and that it is why it occurred to Della to buy Jim a watch fob.
Della would seem to come from a working-class background. Here is a sample of her speech:
“Cut it off and sold it,” said Della. “Don't you like me just as well, anyhow? I'm me without my hair, ain't I?”
Della not only seems to love Jim deeply, but she also seems to look up to him as to a person of a higher social class than herself. She seems to feel privileged to be married to him. He would never use the word "ain't." She wants to buy him a present that would be "worthy" of him, which could mean worthy of a man from his social background.
Jim's character seems to reflect higher social antecedents. He is quiet, reserved, polite, considerate, soft-spoken. Della loves him for being a gentleman as well as for other reasons.
Jim's character is a bit more difficult to describe than Della's character. The reason for that is because he is in the story for less time than Della. Regardless, there are some things about Jim that the story makes clear. First, Jim is young. The story says that he is twenty-two years old. He's obviously married. He has a job, but the reader is not told exactly what his line of work is. Presumably it is some kind of job that would allow him to wear a pocket watch and not be out of place. I figure that it is some kind of clerical job vs. a factory job. Jim is also a calm and quiet individual. He doesn't get angry or accusatory when he comes home and sees Della's cut hair. Despite his meager income, he seems like a fairly positive man as well, because he doesn't come home in a depressed huff. Instead, what is clear is that he deeply loves Della--so much, in fact, that he sold his most valuable possession in order to buy her the combs that she had been wanting. She is the light of his existence.
“I want you to understand me, Dell,” he said. “Nothing like a haircut could make me love you any less."