Historical information

A porthole, sometimes called bull's-eye window or bull's-eye, is a circular window used on the hull of ships to admit light and air. Though the term is of maritime origin, it is also used to describe round windows on armoured vehicles, aircraft, automobiles (the Ford Thunderbird a notable example) and even spacecraft.
On a ship, the function of a porthole, when open, is to permit light and fresh air to enter the dark and often damp below-deck quarters of the vessel. It also affords below-deck occupants a limited view to the outside world. When closed, the porthole provides a strong water-tight, weather-tight and sometimes light-tight barrier (not in the case however).
A porthole on a ship may also be called a side scuttle (side hole), as officially termed in the International Convention for the Safety of Life at Sea. This term is used in the U.S. Code of Federal Regulations. It is also used in related rules and regulations for the construction of ships. The use of the word "side scuttle" instead of "porthole" is meant to be broad, including any covered or uncovered hole in the side of the vessel.

Significance

This porthole is a useful demonstration of naval technology to give people an insight into life at see. Small windows such as this example could be all people would see on long see voyage across rough seas.

Physical description

Commanding officers scuttle made of brass with glass opening window