A tampion is a wooden plug, or a metal, canvas, rubber or plastic cover, for the muzzle

Muzzle (firearm)

The muzzle of a firearm is the end of the barrel from which the projectile will exit.Precise machining of the muzzle is crucial to accuracy, because it is the last point of contact between the barrel and the projectile...

 of a gun

Gun

A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...

. They can be found on both land based artillery and naval guns. Naval tampions have developed into works of art.

Although the cannons of ships of the line

Ship of the line

A ship of the line was a type of naval warship constructed from the 17th through the mid-19th century to take part in the naval tactic known as the line of battle, in which two columns of opposing warships would manoeuvre to bring the greatest weight of broadside guns to bear...

 were protected as they were retracted inside the ships, many smaller vessels had exposed gundecks which required a plug to protect inside of the barrels. Later, the invention of mobile gun turrets meant that all guns were constantly exposed to water. Hence, when not in use, naval guns were protected by wooden, and later rubber muzzle plugs. Typically, rubber and plastic tampions can be shot through in case of an emergency. Plastic tampions are normally designed to be expelled by the build-up of pressure in the barrel as the first shell is fired.

Over time, tampions were embossed or engraved

Engraving

Engraving is the practice of incising a design on to a hard, usually flat surface, by cutting grooves into it. The result may be a decorated object in itself, as when silver, gold, steel, or glass are engraved, or may provide an intaglio printing plate, of copper or another metal, for printing...

with the arms of the unit, and they became collector's items. Nowadays, even warships that typically would not carry heavy guns, such as submarines, have their own badges in the shape of a tampion.