This is a good question. If I had been Norman Gortsby at his age, I probably would have done as he did. But if I had been Norman Gortsby at my present age, I wouldn't have given the young stranger any money regardless of whether I believed his story or not. No doubt Norman himself, if he had been a real character, would have changed as a result of his experience--because he had virtually no chance of getting that sovereign back in the mail. Even if the young stranger had been telling him the truth, he might decide he would rather keep the sovereign than send it back to Gortsby in the mail. (We can't know for sure that it isn't the elderly gentleman who was working the scam, can we?)
A sovereign was a coin worth one pound. One pound in Saki's day was equivalent to five American dollars, and five dollars then would have had the purchasing power of twenty or thirty dollars now.
I have lived in big cities all my life. I often gave money away to panhandlers when I was young, but I came to realize that there are many professionals who can collect a lot of money, especially if they ply their scam in affluent neighborhoods where there is a lot of foot traffic.
Stephen King wrote about a truly successful panhandler who had a terrific location in Lower Manhattan and took in so much money that he didn't even bother to cash in the coins. He was taking in hundreds of dollars a day and paying off one cop to leave him alone. The story is in King's book Hearts in Atlantis.
In one of his Sherlock Holmes stories, "The Man with the Twisted Lip," Arthur Conan Doyle writes about a man who was making an upper-middle-class income as a street beggar.
I have been scammed so often that I am very reluctant to hand over my hard-earned money to anyone. I wouldn't have the audacity to ask people for money, and I can't respect those who do it as a regular practice. I don't even like the feeling that I might have been fooled by a smooth professional--and there seem to be plenty of them in practice these days.