Been collecting data about this gun. Will report shortly!
*Pity we can’t see everything, (shape of butt, etc., front sight missing ) but an interesting example. Could be the Ogino-Ryū school of gunnery; the butt shape would tell us.
(Later)
Small Honda fiefdom in Ōmi called the Zeze Han. Made in 蔓延元年, which is 1860, during the Bakumatsu, towards the end of the Edo period.
The smith seems to be 鈴木鉄造 典貞? Suzuki Tetsuzo Norisada(?) Not sure about the very last kanji…
0.69 caliber in Japanese terms puts it at 1.75 cm, close to a 10 Monme Samurai gun or Shizutsu, a bore larger than the standard ashigaru battlefield gun of 1.5 or 1.6 cm.