A circular or oval opening or window for the passage of light or air. There may be decorative variations on the basic form, including the Four-lobed bull's eye, made up of four interconnecting broken arches.
The Bull's Eye (Portuguese Olho-de-boi) postage stamps were a set of three stamps issued by Brazil on 1 August, 1843. The three stamps with face values of 30, 60, and 90 Reais were the second set of adhesive stamps issued in the world, after the Penny Black and Two pence Blue, to be issued by a country (not just a local issue). Like Great Britain, the design does not include the country name.