O. Henry wanted to show a contrast between the two principal characters, "Silky Bob" and Jimmy Wells, most of which had evolved over the twenty years since they had last seen each other at "Big Joe" Brady's restaurant in New York City. Bob has been extremely successful in crooked enterprises, while Jimmy has not only had humble employment but has actually become a incorruptible policeman.
In order to demonstrate that Bob is well of, O. Henry introduces him about to light a cigar, which is a stereotypical symbol of success.
His scarf pin was a diamond, oddly set.
He doesn't mind showing off his wealth in his apparel. He wants the whole world to recognize him as a success.
The waiting man pulled out a handsome watch, the lids of it set with small diamonds.
O. Henry's story was published in 1905. In those horse-and-buggy days there was no such thing as a wristwatch, and only a minority of men owned pocket watches. There used to be many more clocks in cities, placed there for the benefit of the majority who did not own pocket watches. Some were free-standing clocks with two or four faces. Others were on the sides of buildings, especially churches. Clocks are still seen in the central parts of many cities, but many of them no longer show the correct time, while others do not work at all. Women typically did not carry watches at all. Bob's watch set with diamonds is a glaring symbol of success.
"Did pretty well out West, didn't you?" asked the policeman.
"You bet! I hope Jimmy has done half as well.
Because of the darkness, "Silky" Bob does not realize that the policeman is actually Jimmy Wells. Bob is perfectly at ease because he knows he looks respectable with his diamond scarf pin and his expensive watch. He is undoubtedly well dressed, although O. Henry does not describe his clothing or shoes because these would not be visible in the dark doorway.
When the plain clothes man arrives, pretending to be Jimmy Wells, he asks:
"How has the West treated you, old man?"
"Bully; it has given me everything I asked it for."
So O. Henry has provided ample evidence through description and dialogue that Bob is well off.
O. Henry seems to be suggesting that it is easy to become rich if you are crooked and hard to be successful if you are honest, but that riches do not necessarily bring happiness and that a simple life may be the best choice after all.
O. Henry himself had served three years and three months of a five-year prison sentence for embezzlement, and he had consorted with hard-core criminals in prison and on the outside. Although his experiences gave him much subject matter to write about, he was tormented for the rest of his life by the feeling that he was somehow cut off from the world of respectable people. He used the pen name of O. Henry because he was afraid his real name, William Sydney Porter, would expose him as a felon and social outcast. Many of his stories have the explicit or implicit theme that it is hard for a man to "go straight" after he has started an antisocial career. He shows compassion for people who belong to the underworld because he couldn't shake off the feeling that he was one of them.
O. Henry became notorious as a heavy drinker. He died of cirrhosis of the liver when he was only around fifty years old. This was a loss to American literature, because he was obviously a gifted writer and extremely popular with the public. His drinking was apparently due to his unhappiness and guilty conscience.