1. Water plantain (a.k.a. arrowhead, or omodaka): "a perpetual plant of the water plantain family, was also called shōgunsō (victorious army grass). Because of this martial connotation, it was a design favored for the crests of samurai families" [see: Family Crests of Japan. // Stone Bridge Press, Berkeley, CA, 2007; p. 63].
2. Heron (sagi): "...considered an emblem of longevity, and from China comes the practice of regarding the bird as a mount of the gods and the Taoist sennin. [...] heron also reflects an inauspicious connotation, for the word sagi is homophone for 'fraud' and 'false pretenses'." [see: Merrily Baird. Symbols of Japan. Thematic motifs in art and design. // Rizzoli international publications, Inc., 2001; p. 112]. Some may say, that this is not a heron but a crane (tsuru). It's very possible, and in this case the negative connotation is lost, but the reference to longevity and allusion to sennin remain.
3. Pampas grass (susuki, or obana): as per Merrily Baird, p. 95 and John W. Dower, p. 66, pampas grass is one of the Seven Grasses of Autumn. When combined with flying wild gees, conveys strong autumnal mood.
4. Plum blossom (ume): according to Merrily Baird, the flower has a vast variety of symbolic meanings, including longevity, and a reference to the Chinese Taoists. It is used in 80 family crests [see: Japanese Design Motifs: 4,260 Illustrations of Japanese Crests; Compiled by the Matsuya Piece-Goods Store; Translated by Fumie Adachi. // Dover Publications, Inc., 1972.] Plum is "celebrated for its sweet perfume, delicate blossoms, and habit of blooming at the end of winter".
5. Tree flying wild geese (kari): "Wild geese arrive in large flocks in southern regions during the autumn months, and following their migratory instincts, head back north in spring" [Family Crests of Japan, pp. 85-86]. "The importance of geese in Japanese art was further secured by stories of several military heroes who had achieved victory in battle when a sudden breaking of ranks by flying geese signaled an ambush. The protective role of the birds led to their frequent use in decorating sword furnishings and possibly also their adoption as a family crest motif.Finally, the goose in Asia plays a role in religious traditions" [Merrily Baird, pp.111-112].
6. Hikiryō (line, or bar, or stripe) - a symbol which consists of one, two, or three horizontal or vertical stripes in a circle. "In wartime, Japanese generals [...] surrounded their encampments with huge cloth curtains. Usually these were made of cloth sewn together horizontally and varying in color [...] to distinguish the individual general and his followers. The stripe thus assumed strong martial connotations, and became a mark of identification on personal military gear as well. In the early fourteenth century  the heads of the Ashikaga and Nitta, then the two most powerful clans in Japan, both adopted stripe patterns as a family crest". [See: Family Crests of Japan, p. 111 and John W. Dower. The elements of Japanese design - A handbook of family crests, heraldry & symbolism. // Weatherhill, New York, Tokyo, 1985, p. 144].

1. Hikiryō, see above.
2. Pampas grass (susuki, or obana), see above.
3. Bellflower (kikyo): One of the Seven Grasses of Autumn. "As a crest, it have been adopted among the warriors around the thirteenth century, primarily because of it's beauty" [John W. Dower, p. 48].
4. Four flying wild geese (kari), see above.
5. Weeping willow (yanagi): "It is commonly represented with water, snow, swallows, or herons.  A branch of willow (yoshi) is one of the attributes of the Buddhist deity Senju Kannon (Thousand-Armed Kannon), who is said to use the branch to sprinkle the nectar of life contained in a vase. [Merrily Baird, pp. 66-67].
6. Lone plum blossom in a well frame/crib (igeta, izitsu): "Well crib was one of the most popular motifs in Japanese heraldry".  As a crest it may stay simply for the first character (i) of the family name, however, with a flower inside the well frame, and together with the other symbols present, it may aggravate the sense of autumn-ness. The ten-zōgan dots in this particular case may represent the snowflakes or autumn stars.

Iron tsuba of round form with design of  hatchet, snowflake, and triple diamond in openwork (ko-sukashi), and inlaid with five concentric circles of brass dots (ten-zōgan) and brass inner circular line. Sukashi elements outlined in brass.

Kokusai Tosogu Kai 5th International Convention & Exhibition, October 28-30, 2009 at NEZU Museum, Tokyo, Japan, on page 83 provides the following explanation of the triple diamond symbol: "The pine bark is the form of the Diamonds, "Bishi", mon, seen from Nara period, found on cloth stored in the Shoso In, and used primarily by the Takeda family. The form of Bishi mon [similar to ours] is called "Chu Kage Matsukawa Bishi", (Middle Shaded Pine Bark Diamond)."

"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."

Size: 83.2 x 82.4 x 3.6 mm; 149.2 g

The Carlo Monzino Collection of Japanese sword fittings and swords (Sotheby's, London, 18 June 1996. p. 12-13) №9 provides an illustration of the similar tsuba with the following description: Heianjo tsuba, carved and inlayed with rocks, plants, and waves, also pierced with a jakago [sic] (stone basket).

Gary D. Murtha in his Japanese sword guards Onin - Heianjo - Yoshiro (GDM Publications, 2016) on page 53 shows a look-a-like tsuba (though, with a kogai-hitsu-ana) with the follwoing description: Iron, 77 mm, tsuba with brass tree, snake, jakugo baskets, and curved brass pieces (representing water flowing over rocks). Buddhist halo to reverse. Although showing Onin traits, a Shoami Heiamjo attribution would fit better. Azuchi-Momoyama period.

Iron tsuba of round form decorated with a design of bracken scrolls and paulownia leaves and blossoms (kiri-mon) in openwork (sukashi). Details carved in kebori. Squared rim with iron bones (tekkotsu). Hitsu-ana plugged with shakudō.

Size: 83.6 x 82.9 x 5.4 (center), 5.1 (rim) mm.

Unsigned.

Muromachi period, ca. 16th century.