1.61. A man is riding a subway. He meets a one-armed
man, who pulls out a gun and shoots him. (SJ; from How
Come?)

1.61 answer: Several men were shipwrecked together. They agreed to
survive by eating each other a piece at a time. Each of them in turn gave
up an arm, but before they got to the last man, they were rescued. They all
demanded that the last man live up to his end of the deal. Instead, he
killed a bum and sent the bum’s arm to the others in a box to “prove” that
he had fulfilled the bargain. Later, one of them sees him on the subway,
holding onto an overhead ring with the arm he supposedly cut off; the other
realizes that the last man cheated, and kills him.

1.61a. Variant wording: A man sends a package to someone in Europe and
gets a note back saying “Thank you. I received it.”

1.61a answer: This is just a simpler version; the shipwreck situation is
the same, and the man actually did send his own arm.

1.61b. Variant wording: Two men throw a box off of a cliff.

1.61b answer: Exactly the same situation as in #1.61a (one slight
variation has a hand in the box instead of a whole arm), with the two men
being two of the fellow passengers who had already lost their arms.

1.61c. Variant wording: A man in a Sherlock Holmes-style cape walks into
a room, places a box on the table and leaves.

1.61c answer: In this one he’s wearing the cape either to disguise the
fact that he hasn’t really cut off his arm/hand as required, or else simply
in order to hide his now-missing limb. (from Joe Kincaid)