[orlok]

Originally Posted by Billi

Is the man a scientist? No
Does he get arms regularly? No
Or was this the first and only time that he received an arm? Yes
Does a pathology send him the arms? No
Was a ring on one finger?No

Originally Posted by Billi

And yet another idea: Was it a "false" arm? A false arm in the meaning that some kind of a sign like a tattoo or so was missing so the dead person (I assume the armless is dead) could not be his wife or someone else important to him and that's why he smiled. No

Do I reveal all, or do you want another clue...?

Here's a hint: he was sent the arm by someone who also only has one arm.