Top metal site tube 4. Wooden plug below main barrel. Firing lever at rear of barrel 6. Chips of wood missing on barrel. Not rare, however difficult to find in very good condition.
All cannons are collectibles.
It just depends on what you are collecting. Ones with patent dates are good, as are famous names such as, Swamp Angle, Monarch, Boom, Kid, Dewey, etc. Let's face it, a cannon is fairly easy to make. Cannons have long been popular shop projects, both for high schools, home shops and commercial shops. Many machinist using corporate lathes and equipment have designed and built cannons in their spare time.