A very large and very thin iron tsuba of round form decorated with design of formalized butterfly and dragonfly in openwork (sukashi). The characteristics of the plate resemble those of Kamakura period ko-tōshō tsuba. However, the design seems too 'modern' to me, but it's hard to tell; it may be a late Muromachi or Momoyama period work. Tōshō or Ko-Tōshō school (or a Katchushi). Muromachi period. However, Boris Markhasin and Skip Holbrook insist this is a 20th-century machine-made tsuba. Dimensions: 99.6 x 100.5 x 2.1 mm. This is what Jim Gilbert says about old tsuba:

"Traditionally the old iron plate tsuba are classified into Ko Tosho (old sword smith), and Ko Katchushi (old armor maker) styles. It is sometimes difficult to justify attribution of a given tsuba to the Tosho or Katchushi category. Generally guards with raised rims or relatively complex designs tend to be assigned to Katchushi. This is basically a convention we follow out of habit and convenience." [...] "In Token Kai-Shi part six, Articles by Akiyama Kyusaku, Robert Haynes comments: "…from 1300 to 1400 over 150,000 MOUNTED swords were made in Japan for export alone. This means that over four tsuba a day were made for 100 years. This would mean that at least 3000 persons were making nothing but tsuba, let alone all the other fittings needed to complete these swords. With sword smiths, fittings makers and all the other artists need to complete a sword for export, at least 10,000 sword artists were working together, in any one of these hundred years."

Another tsuba of similar design, Tōshō school, is illustrated in this collection; see TSU-0319.2015. Reference to this design can be found in LIB-1359.2017 Japanese Swords and Tsuba from the Professor A. Z. Freeman and the Phyllis Sharpe Memorial collections, Sotheby's, London, Thursday 10 April 1997; p. 18-19, lot № 37: "A Kamakura-bori Tsuba, Momoyama Period. ...pierced with two large formalised butterflies..."  

Iron tsuba of round form decorated with design of moon, stars, cloud, snowflake, gorintō, and Genji-mon in negative openwork (in-sukashi). Raised tubular rim (dote-mimi). Deep black patina, traces of lacquer. Naka-daka type of plate (thicker in center, getting thiner towards the rim). Visible gap between the rim and the plate. Dimensions: Height: 91.7 mm; Width: 90.8 mm; Thickness at seppa-dai: 2.5 mm, plate before rim: 2.2 mm, of the rim: 5.6 mm. At least Mid Muromachi period, 15th century, but possibly earlier. In 'Silver Book', commenting tsuba №34 Sasano writes: "The technique used to create the rim is the same used for the peak (koshimaki) of helmets (kabuto) during the Kamakura and Nanbokucho periods." On the other hand, the abundance of sukashi elements points towards later times, perhaps late Muromachi or even Momoyama period. "Gorintō is a grave stone composed of five pieces, piled on one the other, representing, from the bottom upward, earth, water, fire, wind, and heaven, respectively" [Nihon Tō Kōza, Volume VI, Part 1.  AFU, 1993, p. 6. / LIB-1554]. A romantic description of the piece may look like this: The air is scented (incense symbol); it's a graveyard, marked by gorintō; a winter (snowflake) evening or night (moon, stars); mist is rising from a ravine towards moon. I did not manage to find a katchūshi piece of this design, only a few Kamakura-bori tsuba:   While the upper tsuba is dated the end of Muromachi, the lower is attributed to the 17th century - Momoyama or early Edo period, though the author put this attribution under question. Deciphering of the strangely shaped opening to the left of nakago-ana is sometimes "a conventional scroll", and sometimes - a fern or bracken. I think mine is a cloud or mist, but I don't have any material evidence to prove this understanding, and I came to a conclusion based only on context. It may easily be dinosaurs playing ball. The fact that this thing always accompanies the Genji-mon, or incense symbol, it may be a scent itself.

Iron tsuba of half round and half lobed (chrysanthemoid) form decorated with plants and family crests (mon) in cast brass inlay (suemon-zōgan), and scattered brass dots inlay (ten-zōgan); brass wire inlay outlining the rim, seppa-dai, and hitsu-ana (scalloped wire) on both sides. Surface treated with hummer punch marks. The chrysanthemoid half of the plate chiseled  with thin shallow grooves, outlining the petals. Copper sekigane. On the face the inlay represents: mandarin orange (tachibana), half karahana, encircled bellflower, and four encircled three-stipe family crest (mitsubiki-mon of Sakuma and Abe clans, and some others). On the reverse the design is similar but two of the mitsubiki-mon symbols replaced with two comb-shaped Genji-mon ideographs. Ōnin school. The end of mid-Muromachi period, beginning of the 16th century. Size: 74.3 x 72.7 x 2.4 mm.  

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

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.