Reminds me of when I read the Hebrew translation of Pippi Longstockings back in elementary, and there was a scene in which two burglars play dumb (if I remember correctly) and say they just wanted to know what ‘the clock’ was, so she explains to them what a clock is. In Hebrew the term is ‘ma hasha‘á (מה השעה, ‘what is the hour’), but it said ‘what is the clock’ and explained the phrase in a footnote, and it really amused me.
I think "What is the bell?" should be an acceptable solution. While it is literal and the sentence is usually meant in a different sense, it is still a possible solution. For example, in a story, there could be a series of objects that look like one thing but are actually another. "The spoon is a salt shaker, the fork is a telephone, what is the bell?"