The chrysanthemoid (kiku-gata) iron plate with polished surface decorated with arabesque (karakusa) and paulownia (kiri) leaves and flowers in brass, copper and silver flush inlay (hira-zōgan) on both sides. Some of the inlay goes over the edge. Kozuka- and kogai-hitsu-ana are filled with lead plugs. Sekigane of copper. Chrysanthemum and paulownia are the symbols of imperial family. The face is signed: Izumi no Kami to the right of nakago-ana, and Yoshiro on the left; the back is signed Koike Naomasa. His signed work is considered by many experts to have been made-to-order only. The original wooden box (tomobako) with inscription (hakogaki) signed by Dr. Kazutaro Torigoye and dated Showa 39 (1964). The late Muromachi or Momoyama period, 16th century. Dimensions: 89 mm x 84 mm x 3.6 mm; Weight: 170 g. Hakogaki lid: Yoshirō  kikka-gata Hakogaki lid inside: Iron, signed on the omote: Izumi no Kami – Yoshirō; on the ura: Koike Naomasa. Kikka-gata, pronounced maru-mumi, two hitsu-ana, karakusa, and kiri design in brass, silver, and suaka hira-zōgan. Height 8.5 cm, thickness 3.5 mm. Herewith I judge this work as authentic. On a lucky day in July of 1964. Torigoe Kōdō [Kazutarō] + kaō According to Robert Haynes [Catalog #7, 1983; №32, page 42-43] "This full form of the signature is seen very rarely". His example, illustrated in that catalogue, measures: height = 86 mm, thickness at seppa-dai = 3.75 mm and signed Izumi no Kami Yoshiro on the back and Koike Naomasa on the face. The further description of his specimen by Robert Haynes:

"Early signed example of the work of Koike Naomasa. The kiku shape iron plate is well finished. The flush inlay is brass, for the scroll work on both sides, with the leaves and kiri mon in brass, copper and silver with strong detail carving. Some of the inlay goes almost over the edge, which is goishi gata. The large hitsuana are plugged in lead with starburst kokuin surface design. [...]The face is signed in deep bold kanji: Koike Naomasa; the back is signed: Izumi no Kami, on the right and Yoshiro on the left. There are one or two small pieces of inlay missing. Sold by Sotheby London, Oct. 27, 1981, lot 368. Height = 86 mm, thickness (seppa-dai) = 3.75 mm, (edge) = 4 mm."

Another similar example presented at: "Tsuba" by Günter Heckmann, 1995, №T55 — "Designation: Koike Naomasa. Mid Edo, end of the 17th century. Iron, hira-zogan in brass, copper, silver and shakudo, katakiri-bori. Tendrils and leaves. 87.0 x 78.0 x 4.0 mm." Reference: Japanische Schwertzierate by Lumir Jisl, 1967, page. 13. [SV: Actually, his tsuba is signed Izumi no Kami  Yoshiro on the back; and Koike Naomasa on the front, exactly as Robert Haynes's tsuba. Dating this tsuba Mid-Edo, 17th century may be considered a misattribution]. More details regarding the Yoshirō tsuba. 

Iron tsuba of round form inlaid with brass and shakudo (suemon-zōgan) with a design of tendrils, leaves, double gourds, and folding fan with two wild geese on the face and the same design only with a fan with two interlocked rings (wachigai) on the back. Design is supplemented with a round family crest (mon) of three fans in openwork (sukashi). Hitsu-ana and the mon are outlined with brass rope. Copper sekigane.

Some attribute such tsuba as belonging to Heianjō or even Yoshirō School, and date them to Momoyama period. I keep this piece under Ōnin rubric, late Muromachi, but this is just a question of personal preference.

Some inlay is missing, some repaired; traces of rust. Otherwise - decent condition.

Late Muromachi period (1514-1573). Size: 77.4 x 77.1 x 3.8 (center), 3.2 (rim) mm