Thanks for the guesses. My thought when I first saw this tsuba was Higo Kamiyoshi. The previous owner also thought it was Higo. He submitted it to NTHK and received something else, so he submitted it to the NBTHK, but received the same attribution as NTHK.
Both attributions came back as SHOAMI.
By the middle of the Edo period the Shoami style had lost much of its popularity. The rise of Bushu and Choshu tsuba, as well as the new kinko schools further reduced the prestige of the once great Shoami. They ended up copying the style of more popular schools and this is perhaps where the Higo influence came from (or Tosa Myochin or Akasaka perhaps).
I enjoyed reading your comments and would like to put up another tsuba for kantei if you’re interested.