MauroP

Yamashiro jū Shigenobu saku (山城住 重信作), possibly Shōami school.

Here the hakogaki (I'm not shure about the date): 葵形鉄地影透 * aoi-gata tetsu-ji kage-sukashi 銘馬面序政花押 * mei Bamen Tsunemasa kaō 昭和壬子年弥生 * Shōwa mizunoe-ne-nen yayoi [March 1972] 寒山誌 * Kanzan shirusu (+kaō) Would you mind to post an image of both sides of the hakogaki? (I'm collecting images from hakogaki by Satō Kanzan)

Kaga-kinkō or Shōnai-kinkō?

100% agree with what Dale says. If a tsuba fits a Shōami attribution this is one (and many doesn't...)

Usually the two collaborating artisans signed each on the opposite sides of the tsuba. What about your tsuba, Grev?

Not so strange in Nanban tradition, as you can see in the tsuba I already posted.

I have another hypothesis (explained with Venn diagrams)...

Nanban and Hizen attributions overlap for a certain extent (though some tsuba are clearly Hizen and not Nanban). Jakushi could also be be a legit call, but usually Jakushi tsuba are signed and the vast majority of them represent dragons or Chinese landscapes. A non-toban shape of seppa-dai makes me lean towards a Nanban attribution (but don't take any attribution too seriously...).

The inlays look quite amatourish, possibly a Shōwa period tsuba?

Have space aliens ever landed on Earth? Who knows... Possible? Yes, of course! Likely? No, of course! Have iron tsuba been casted in Edo period? The same as above... that's all IMHO.

Markus Sesko's "Signatures of Japanese Sword Fittings Artists" lists 3 Nobukuni and 5 Masatoshi entrances, but never together...

I was quite puzzled by the attribution of this tsuba to Hirata (平田), as in my understanding, the Hirata school is typically associated with suaka, yamagane, or shinchū-ji tsuba, often featuring shigure-yasuri or okina-yasuri file marks, and sometimes an odawara-fukurin. So, I did a bit of research and found that most "Hirata" attributions seem to originate from Bonhams auctions. None appear to be papered by the NBTHK, and only a few are signed by Hirata Harunari (8th generation, late Edo) or Hirata Haruaki (Meiji period). Perhaps there is some confusion with Hirado (平戸)? Here some images: 1. signed Narikazu (hard to believe he's the 2nd generation Hirata master) 2. a typical Hirata piece 3. a shippō-zōgan tsuba papered as Hirado 4. a similar piece papered as Nagasaki shippō

I wish to suggest Nagasaki shippō as a more likely attribution...

Dan, please go here and read all the stuff... https://www.openmovportal.ca/argus/final/Portal/Main.aspx?component=AAFG&record=a7450643-c397-4d2e-a9a6-0cea5b180791

Thanks God the Museum of Vancouver also states that the material is copper and/or silver alloy (?). So no iron casting involved (or clearly the museum curators don't know anything). https://www.openmovportal.ca/argus/final/Portal/Main.aspx?component=AAFG&record=a7450643-c397-4d2e-a9a6-0cea5b180791