Bird in a Cage Engraving
There are two images (a bird and a cage) that are engraved on a case of a gas lighter.
The engraving hints at a thaumatrope, an optical toy in form of a disk, each side of which has an image. When it is twirled quickly, the two pictures appear to blend into one.
The bird’s form resembles fire, the cage’s — the lighter itself.
Such a Zippo is even more pleasant to spin in hands.