The subject could be so immense that some limitations are in order. The first limitation is in the subject itself. It is about identifying tsuba from schools which did not usually sign their pieces, as were the case with most early schools, and not identifying the maker of an unsigned tsuba who usually signs, which is the case with most Edo period kinko. As we know in fact very little about the reasons why occasionally they did not, and I have found a contradiction to every explanation forwarded, I shall further limit myself to the main schools of tsubako. The smaller and lesser schools, as well as the unrecorded independent will be left aside to keep this discourse within reasonable limits.

Two other limitations are not of my choice. The second is 'not knowing'. The exact attribution of early cast tsuba, the true distinction between ko-kinko, ko-Goto, ko-Mino, etc., what are the so-called ko-Shoami sukashi tsuba, how much confusion between (among others) Hayashi and Nishigaki tsuba; all the answers to these questions are at best vague, and should be taken with scepticism until information is more accurate. The third is that this article being meant to be used as a guideline for beginning collectors, especially on the subject of sukashi schools which are the most difficult, I refer to classic styles and average sizes (each school being averaged in that respect over 20 to 30 tsuba). Real tsuba vary around the given figures, and worse there are always exceptions to a general rule, the more general the rule, the more exceptions are likely to be met. Usually they can be identified (with room for doubt) by experience and comparison. Connoisseurship is acquired the hard way, by study, discussion, handling a lot of pieces, not with a single lecture, or reading a book.

A few words now about the use of this article and what to expect of it and, most important, what you cannot expect. This article is meant to provide the student with a methodology, which is used over and over to identify unsigned pieces, will provide after time, what is called a connoisseurs eye, an experienced feeling of styles and details which will enable him, in most cases, to move straight to the right answer. But keep in mind that without sufficient practice you will have the unpleasant feeling that nothing useful has been said here. Keep also in mind that nothing is universal or foolproof. After much experience you will learn, at connoisseur's level, finding the proper answer is easy 85% of the time, needs some research 10% of the time, and that 5% is truly a matter of opinion, which makes all the fun. One other major limitation is my own: During the preparation of this paper, even with the aforementioned limitations, I decided to leave the soft metal tsuba for another time and limit myself to iron tsuba. Time divisions and technical terms have been published over and over, so I will consider them as known, as I do not vary from the classic. But in the area of sizes I have adopted a non-standard vocabulary (there isn't any) and therefore needs defining:
Thickness:  Very thin: under 3.5mm  Thin: over 3.5 and under 5mm  Medium: from 5mm to under 6mm  Thick: 6mm and over
Size:  Small: under 75mm  Medium: between 75 and 85mm  Large: between 85 and 100mm  Very large: over 100mm

There are two ways to proceed in identifying the school of a given tsuba: the global look and the slow process of working from the edge to the seppa-dai. The first is more suitable for the soft metal tsuba, the second is necessary for the iron tsuba. If you have worked correctly: by the time you reach the seppa-dai, you should know enough to put a name on the tsuba, which is the game that is played here. In both cases, the student should work by the method of elimination; list the possibilities, cross out at each step the unsuitable schools, usually at the end you will end up with one answer. Not too rarely you will end up with none: you have tried your skill on one of the aforementioned exceptions. Back to square one, and try to determine the characteristic that should be disregarded. Connoisseurship is finding the right one. The alternate and most commonly employed attitude is dumping the piece in the ever-convenient Shoami bag. But it is time for serious study. There are two charts located at the bottom of the TSUBA web page for convenience which will make things simpler than they might sound. I shall use a description of the various schools one by one, in an order which I hope will be helpful to most.

TOSHO TSUBA:
They are medium sized, very thin, the rim being thinner than the seppa-dai (1.8 and 2.7mm). They have only ko-sukashi.

KATCHUSHI TSUBA:
They are also very thin (2.6mm at the seppa-dai) but have raised rims of various kind. They come also in various sizes from medium (in this case only ko-sukashi is used) to very large (over 100mm). In the case of the large type we find both ko and ji-sukashi and the latter both in yo and kage technique ( yo-sukashi is positive silhouette used in the ji-sukashi method, kage-sukashi is negative silhouette used in the ji-sukashi method ). Incidentally, the first Suruga comes straight out of the katchushi (he is a Haruta), but his work is characteristically different. He makes very thin tsuba in medium to large size, with no raised rim, in yo ji-sukashi. As all the following Suruga he uses original large kuchibeni ( sekigane ). The second, also in katchushi style reverts to ko-sukashi, while signing Bizen Suruga, the following using Inshu Suruga. Also branching from the katchushi are the styles of Kamakura-bori, very thin, medium sized with or without ko-sukashi, carved in low relief, and Onin, very thin, small size at the beginning, rising later to medium with brass inlay which we shall discuss more completely later. The yo-sukashi schools are the most difficult, part from lack of information, part because they took designs from one another back and forth. It will therefore be very important to single out the measurable differences, such as size and thickness at the rim and seppa-dai, to separate the schools.

KYO-SUKASHI:
The most numerous, and the easiest to identify: medium sized (80mm), thin (4.8mm), they have repeated over and over the same designs in large quantities. Rounded shape, with occasionally a bamboo stalk design rim. They have a very open air and elegant aspect. One other type of tsuba directly connected to the kyo-sukashi are the so-called ko-Hagi of the Momoyama period. Though they are in marubori, they have all the same designs easily recognizable, copied from a classic kyo-sukashi design and share the other characteristics. The tsuba in this style were made in Kyoto and are the product of the Kyo-sukashi school.

THE OWARI GROUP:
This group has a common characteristic shared by no other group. The thickness at the center is substantially inferior to that of the rim. The appearance is in general more rustic than the other groups. The designs are either figurative or abstract, some of them very difficult to identify. Three schools belong to that area.

Owari Tsuba:
On the average smaller (77mm) but thicker (4.9 at the center, 5.7 at the rim), the rims are usually of rounded square shape and show on the early tsuba fine granular tekkotsu, which becomes scarcer in the Momoyama era and disappear later.

Kaneyama Tsuba:
Slightly smaller (75mm) and thicker (5.1 at the seppa¬dai and 5.7 at the rim), their rim is usually squarer than the previous group and the granular tekkotsu is coarser.

Yagyu Tsuba:
This is the last Owari sukashi group. It appears in the Genroku period and lasts into late Edo. Even smaller (72.5mm) and thicker (4.75 to 5.75) their designs are very rustic and strong in appearance, the earlier examples having linear tekkotsu on the rim, which are rather squarish.

THE HIGO GROUP:
Hayashi and Kamiyoshi Tsuba:
Medium size (78mm), medium thickness (5mm), the rim is rounded and integrated in the design (pine branch or bamboo stalk), they only do iron sukashi, and they are the only ones to use superficial decoration on it: occasionally gold or silver nunome. The edges of their sukashi are rounded (called "Memwo Toru"), the designs are naturalistic, heraldic, or ornamental. The first Kamiyoshi is a pupil of the 3rd Hayashi and his work is not clearly distinguished from the latter. The second and third Kamiyoshi signed many pieces but the unsigned ones are recognizable by the tagane marks ( punch marks left around the tsuba's nakago ana to facilitate a tight fit of the tsuba on the sword ) around the nakago ana.

Kanshiro Tsuba:
Slightly smaller (76mm) but thicker (5.6mm), their designs are naturalistic and the edges of their perforations are sharper. No surface decoration. Their sukashi work is not as refined as the Hayashi, but they make up for it with their superb soft metal work.

Hikozo Tsuba:
His iron work is very rare. The plate is medium sized, very thin, and the openwork is easily recognizable by the curved one-sided slant of the openings.

SHIMIZU (Jingo) Tsuba:
Only the first two did not sign. Their sukashi work, if it exists, is exceedingly rare. They do Suemon zogan on beautifully hammered iron plate. The plate of the first is very thick (over 6mm), that of the second noticeably thinner (5mm). The quality of the last is by far the best. They do also Sukidashi-bori with silver or gold nunome of animal subjects.
Before leaving Kyushu, I shall just mention one of the neglected groups: the Namban tsuba, because they are easily recognizable, well known, and have foriegn influence of artistic merit.

AKASAKA Tsuba:
This is the last, with their branch school of Tosa Myochin, of the important sukashi schools. Of small medium size (73.5mm) they are thick with a slight tendency towards sloping at the edge (6.2-6.1mm) which are rounded or rounded square. The designs are naturalistic, sometimes rather abstract. The three first did not sign and combined influences of the Owari and Kyo styles, while the later generations signed often and were influenced rather by the Higo style. The Tosa Myochin often signed, but their numerous unsigned pieces are identifiable by the slanting tagane marks on the top of the nakago ana. They are very close in style to the 4th and 5th Akasaka. I shall just mention the numerous "Bushu tsuba" of indistinct origin, even the minor artists being in the habit of signing in the Edo period.

BRASS INLAY:
Onin:
We have already mentioned the Onin zogan. The characteristic of their inlay is that the subject is cast in low relief separately and then inserted in a cavity carved out in shape. The result is that the inlay is not very securely attached to the plate which explains the numerous missing inlays we find on their tsuba today. The earlier types are small and use only dot and line inlay (Shinchu ten zogan), the slightly later are middle sized tsuba with floral and stylized designs in a larger surface (Shinchu Suemon zogan).

About TEKKOTSU:
They are lumps of iron with a higher carbon content than the surrounding iron. Being harder they protrude, mainly on the outer edge, as a result of hammering. They appear mostly on guards of the Muromachi period, less in Momoyama, disappearing on Edo period tsuba. The reason for this is not clearly known, neither if their appearance is intended or not. The usual version is that tekkotsu gives the guard a more rustic and manly appearance, which appealed to the taste of the warriors of the fighting ages. This is implied in the fact that when forgeries are made to imitate early sukashi tsuba in the turn of the century, tekkotsu are faked by being carved. But I have a strong inclination toward another view: tekkotsu are simply the result of wear. Two reasons for this: first I have seen several unquestionably Muromachi Owari sukashi tsuba in mint condition with no trace of tekkotsu. Second the lower carbon content iron is softer than the higher carbon content iron, therefore wear will cause the high carbon content iron to stand out after a length of time of use, which is the case of early tsuba. Also the higher the carbon content the lesser the tsuba will be subject to rust which eats the iron away. Therefore it is normal that treasured Muromachi tsuba, well preserved, should show no signs of tekkotsu.