Bob has apparently had the nickname "Silky" Bob since he and Jimmy were young men over twenty years earlier. The name "Silky" has at least two connotations. One is that he has a taste for luxuries such as silk shirts, silk pajamas, silk scarves, silk underwear, and silk handkerchiefs. The other connotation is that he is a smooth character. Together these two character traits could easily lead him into a life of crime, since he would need money to gratify his expensive tastes. He does not seem like the kind of criminal who would commit violent crimes. More likely, he has been a confidence man, like some of O. Henry's characters in other stories. He displays his smooth character by the way he talks to the policieman, even though he is a wanted man.
"It's all right, officer," he said reassuringly. "I'm just waiting for a friend. It's an appointment made twenty years ago. Sounds a little funny to you, doesn't it? Well, I'll explain if you'd like to make certain it's all straight. About that long ago there used to be a resturant where this store stands--'Big Joe' Brady's restaurant."
And while "Silky" Bob is providing an exposition of the plot line to the officer, O. Henry is characterizing him as a smooth talker. The fact that Bob is wearing a diamond pin in his scarf and flashing an expensive pocket watch displays his taste for luxuries.
There can be no doubt that Bob is the more imaginative of the two men. He tells the policeman, whom he doesn't recognize as his old friend, that Jimmy was "a kind of plodder, though, good fellow as he was." On the other hand:
"I've had to compete with some of the sharpest wits going to get my pile. A man gets in a groove in New York. It takes the West to put a razor-edge on him."
No doubt, Bob has used his imagination to invent all sorts of schemes to get rich quick. He has probably sold worthless stocks and bonds. He does not mention a specific part of the West where he has operated, so it seems that, like most confidence men, he has found it wise to keep on the move in order to avoid running into irate former customers who might want to tar and feather him. That would explain why he doesn't mind traveling a thousand miles just to have dinner with an old friend in New York City.
Jimmy Wells has lived a conventional life. He may have shown more wisdom but not more imagination. He is probably married, has a little home, a wife who is a good cook, and several children. He does not show any unusual imagination in the way he has his friend arrested. He doesn't outwit "Silky" Bob but just acts as an ordinary beat cop would act in a similar situation.