Shabbat 59 - Jerusalem of gold
An animal should not go out in a public area with a bell around its neck, whether sounding or stopped, because it looks as if the owner is taking it to the marketplace. Incidentally, this bell is susceptible to ritual impurity. But in another place we learned that is not susceptible!? - Not a problem: the first case is when it has a clapper, and the second one is when it does not. But why should this be the case? It is either a utensil or it is not, with the clapper or without!? - That is exactly the point, without a clapper it is not fit for its original purpose.
To illustrate, consider a metal shoe of an animal. For impurity, what use can it be fit for if not worn by an animal? Rav says, to drink from it in battle; Rav Chanina says, to anoint oil with it for the battle; Rabbi Yochanan says, to use it to flee from battle, stepping over thorns. Their disagreement is about how close to the original use does the new use have to be. The differences between them emerge when it is dirty (you won't drink from it) or when it is heavy (you won't run in it).
"Jerusalem of gold" was a golden ornament with the likeness of Jerusalem, like the one Rabbi Akiva fashioned for his wife. Can a woman wear it on Shabbat? Some say that it is burden and she would violate the Torah; some that it is an ornament, but it is prohibited, since she can show it off to her friend, and then carry; and some - that it is completely allowed, since a prominent women wearing it won't take it off to show.
Art: Anthonie Palamedesz - A gentleman offering a piece of jewelry to a woman