The Armstrong Cannon was a powerful rifle-bore breech loading cannon. Not an actual model but a design

Sagahan Armstrong gun used at the Battle of Ueno against the Shogitai 1868

Photo of actual armstrong cannon used during Boshin War.

lineage, the armstrong lends its name to it's English inventor, Sir William Armstrong. Being made of wrought iron and later steel the Armstrong cannon was far lighter and portable compared to previous artillery pieces, thus the weapon could be carriage towed or flush mounted on naval ships. The weapon was used around the world extensively, the American Civil War (where both sides used the cannon), the Opium Wars, and the Boshin War.