Round iron plate of grey colour decorated in low relief (sukidashi-bori) on the face with sea waves (both layered waves, seigaiha, and rough waves, araumi), sago palm (cycas revoluta, sotetsu), presumably orchid leaves (ran) - five of them - hanging from the above, and  reeds (ashi), and on the back with waves (seigaiha only), rocks, chrysanthemums (kiku), clove (chori), reed, and presumably orchid leaves - three of them - hanging from the above. The kozuka-hitsu-ana was probably cut later. The plate is lacking the raised rim, typical for the kamakura-bori school. Muromachi period.  Dimensions: Height: 76.8 mm, width: 76.1 mm, Thickness at seppa-dai: 3.3 mm, at rim 2.0 mm. Height of nakago-ana: 29 mm. Weight: 82.4 g. NBTHK certificate № 402152: Hozon - "Worthy of preservation". A similar (most probably the same) tsuba is illustrated and described at Butterfield & Butterfield. IMPORTANT JAPANESE SWORDS, SWORD FITTINGS AND ARMOR. Auction Monday, November 19th, 1979. Sale # 3063 under lot № 66. It describes the piece as following: “Kamakura bori work of the Muromachi period. Round thin plate with some small iron bones in the edge. Carved with design of plants (sego palm) rocks, and waves on the face. The back has half of two chrysanthemums, waves, clove, and sego palm leaves. The kozuka-hitsu has been added and later enlarged. A good typical example without the rim most have. Diameter: 7.7 cm., thickness 2.5 mm. Estimated price $100-200":

Iron tsuba of six-lobed (mutsu-mokkō-gata) form, with six wild boar's eye shape (inome) openings (sukashi). Hitsu-ana and the entire perimeter of tsuba have typical for this school raised rim. Lobes are decorated with landscape motifs in low relief carving (sukidashi-bori). On the obverse: A hut under a full moon, Shinto shrine gates (torii) with pines and a full moon, rocks, a large pine tree, and a temple (pagoda) surrounded by rocks and waves. On the reverse: waves, fishing boat, wild gees in flight under full moon, maple, hexagon (tortoiseshell, kikko) with a dot inside and a dot outside (inclusion/exclusion symbol), and chrysanthemum (the last two may be family crests, mon). Kamakura-bori school. Late Muromachi period (1514-1573). Height: 64.2 mm, width: 74.3 mm, Thickness at seppa-dai: 3.2 mm, at rim 2.6 mm. Weight: 62.8 g (light). NBTHK old green certificate №561: Tokubetsu Kicho  - "Extraordinary Work". A look-a-like tsuba can be found at the Compton Collection, part II, pp. 14-15, №17, though his tsuba is more massive (80 x 84 x 4 mm). NBTHK paper says that the motif is Hakkei (八景), i.e. "Eight Views," so several interpretations are possible (the original Chinese ones, Omi Hakkei, etc.).  However, most likely it is the 'Eight views of Omi' (近江八景  - 'Omi Hakkei'). Why the artist selected a 6-lobed form for depicting 8 views remains unclear, and thus we are in our right to raise the question whether the motif is indeed Hakkei. The term Omi hakkei (eight views of Omi) refers to painting or print sets which illustrate life on the shores of Lake Biwa in Omi (now Shiga Prefecture). The model for such paintings came from China, where, from the eleventh century onward, painters had produced eight views of the Hsiao and Hsiang lake areas of Hunan Province. The themes, which follow the original Chinese models, are: geese descending to land, returning fishing boats, clearing rain, a snow-covered evening landscape, the autumn moon, night rain, a temple bell at evening, and the glow of sunset. Japanese artists have also used the eight-theme approach for other parts of country - including cities - and applied it to subject matter other than landscapes. [Merrily Baird. Symbols of Japan. Thematic motifs in art and design. Rizzoli international publications, Inc., 2001, page 308-9]. Japan Encyclopedia by Louis Frédéric also mentions Omi Hakkei as "Eight landscapes of Omi", and states that this theme was often cited in poetry after 1500. It is likely that the tsuba in focus is designed under the influence of the theme popularity in the 16th century. The theme was effectively exploited by prominent ukiyo-e artists Suzuki Harunobu and Utagawa Hiroshige in the 18th and 19th century, respectively. These are the eight scenes of the theme (see Wikipedia):

• Returning sails at Yabase (矢橋の帰帆) - Yabase. Yabase is an old harbour on the east side of the lake. Near the Tokaido, it was used for a shortcut to Otsu by boat.
• Evening glow at Seta (勢多（瀬田）の夕照) - The Chinese Bridge at Seta. The long bridge across the Seta was used by the Tokaido. In the background the "Fuji of Omi", the Mikamiyama. It is just above 400 m, but indeed well visible.
• Autumn moon at Ishiyama (石山の秋月) - Ishiyama Temple. The Ishiyamadera was located on a hillside next to the Seta River. It got his name form the strange rocks on which it is built, partly on supporting beams. A hut at the upper end of the site allows a view of the lake, and the moon.
• Clear breeze at Awazu (粟津の晴嵐) - Awazuhara. Awazu is well known for its pine wood, Awazu-ga-hara.
• Evening bell at Miidera (三井晩鐘) - Mii-dera. Miidera temple was built in the 8th century. Its famous bell is one of the "Three bells of Japan", the other two being those at Byoodo-in, Uji and at Jingoji, Kyoto.
• Evening rain at Karasaki (唐崎の夜雨) - Karasaki Shrine. Karasaki is a small cape with a single large pine tree, a hitsu-matsu.
• Wild geese returning home at Katata (堅田の落雁) - Ukimido. Alighting geese cannot be seen always, however the little temple near Katata in the square hōkyō-style, detached from the lakeside, connected by a bridge. The first part of the name uki is the same as in Ukiyo-e, meaning floating. Midō means temple.
• Evening snow at Hira (比良の暮雪) - Hira Mountains. The Hira mountains on the west side of the lake experience the hard winter, when the winter monsoon brings much snow from the continent.

In any case, as a conservative, I say that it is a landscape motif and a late Muromachi period work, rather than Omi hakkei motif and a mid-Muromachi work.

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.