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. 

Thin iron tsuba of round form with design of family crests (mon) and arabesque (karakusa) in brass or copper inlay (suemon-zōgan) and occasional scattered brass dots or nail heads in ten-zōgan. Seppa-dai outlined with brass wire in the shape of a rope; kozuka-hitsu-ana outlined with scalloped brass wire. Rounded rim with iron bones (tekkotsu). The surface covered with lacquer (urushi). Ōnin school. Late Muromachi period, 16th century. Family crests on the face: 1:30: Two lines (double stripe) encircled (maruni futatsu biki). 4:30: Stylized clove (choji). 7:30: Divided rhombus, or four lozenges incorporated in one (wari-bishi); it is also called Takeda-bishi, the family crest of warrior Takeda Shingen (among the others). 10:00: Stylized Genji-mon (Genji kō-zu) or incense symbol. On the reverse: 2:00 - "Chinese cloud" not a crest. 5:00: Bit (Kutsuwa) 7:30: Number four in a fan (ōgi-san) 10:30: Two dots in a well frame (igeta).      

Shingen school (or style) tsuba of round form with an iron core of spoked-wheel shape, with its centre covered with a copper plate decorated with star-shaped punch marks. From this copper plate outward, the body is formed by brass and copper wire (flat and twisted) in a weave pattern. Both hitsu-ana are outlined in brass with a raised rim. Copper sekigane. Unsigned. Edo period, 18th century. SOLD   Height: 98.0 mm, Width: 97.4 mm, Thickness at seppa-dai: 6.0 mm. Weight: 290 g. NBTHK certificate №436696: 'Hozon' attestation. Citing "JAPANESE SWORD-MOUNTS IN THE COLLECTIONS OF FIELD MUSEUM" by Helen C. Gunsaulus, Assistant Curator of Japanese Ethnology. 61 plates. Berthold Laufer, Curator of Anthropology. Field Museum of Natural History, Publication 216, Anthropological Series, Volume XVI; Chicago, 1923; p.45: "An unusual group of tsuba popular in the late sixteenth century and afterwards is made up of those guards known as Shingen tsuba, a name which was derived from a sixteenth-century warrior, Takeda Shingen (Takeda Harunobu, 1521-73), who is said to have preferred this style of guard, as it combined strength and lightness. Under the category of "Shingen", four different types abd generally listed, though a fifth appears in the drawings in the Boston Catalogue of Okabe Kakuya "Japanese Sword Guards" (p. 21). It is square, that form which is said to have been used in Ashikaga days for scaling walls, the sword having been set up as a step. [...] The following descriptions include, however, the Shingen tsuba usually met with.

1. So-called Mukade ("centipede") tsuba are made of iron in which a centepede is inlaid in brass or copper wire. Mukade tsuba of Myōchin and Umetada warkmanship have been found with the inscription, "Made to the taste of Takeda Shingen".
2. There are those of solid iron, with need centers of brass, to the edges of which is affixed a weaving of brass and copper wires which is bound to the foundation disk by a rim, usually decorated simply.
3. Another type is of solid iron, bored at intervals and laced with braided or twisted wires of copper and brass.
4. The fourth type is a chrysanthemoid form, chiselled in open work and laced or woven tightly with copper and brass wire."

I believe that my tsuba [№ TSU-0338] belongs to the fourth type. However, this particular specimen does not conform with the description of Shingen tsuba as combining strength and lightness. Its weight is 290 g, which tells us that most probably it had purely decorative function (as most tsuba in Edo period). A somewhat similar design can be found at wikimedia. A look-a-like tsuba is illustrated at Compton Collection, Part II, p.p. 26-27, №54. It is dated ca. 1700. It was in a box with Sato Kanzan inscription, and had NBTHK certificate attesttion of 'Tokubetsu Kicho'. Price realized: $5,280.