Owari sukashi tsuba 尾張透鍔. I believe this tsuba dates to the early Edo period (江 戸初期時代 Edo Shoki Jidai). The iron is an excellent black colour with rich purple under tones and well forged with some fine surface texture. There are no tekkotsu but the mimi has some modulation. There are Ryohitsu Shitate (両櫃仕立) that are an interesting shape. The kozuka hitsu 小柄櫃 is large and elongated and would suit quite a big kozuka while the kogai hitsu 笄櫃 is a bit smaller. It is an interesting square design seen on Edo period Owari and Shoami tsuba. The mimi is fine and broad and makes this smallish tsuba look very powerful.
The design is Kiri no Zugura 桐の図柄 or a paulownia flower design. The 3 larger bodies that take up the lower left of the design are the leaves and the three kiri flowers are at the top right. This is a very common Owari design. The dimensions are 71mm x 70mm x 7.6mm.
There has been for some time, debate on both sides for tagane ato to be a form of signature. This is actually well documented in groups like the Higo and Akasaka schools but guards made in small shops or by individual artists that have little or no recorded history will only ever be speculation. The tagane ato or punch marks that surround the nakago ana on this tsuba however are very distinctive. An almost identical tsuba is published in 刀剣・小道具類 Token, Kodogu rui. Items of Token and Kodogu. 公開入札 オークション Kokai-nyusatsu, (auction open bid, auction) 全国美術 刀剣青年会 Zenkoku Bijutu-token seinen-kai (National art swords young men’s association). These tagane seem just too similar to be random, one has to wonder if they were produced by the same hand ?, or at last to have come out of the same shop. To produce at least 2 tsuba with this much detail in the tagane would suggest purposeful intent, and may well be the calling card for this particular tsubako.