This is a very large tsuba worked in something very like Kyo-sukashi style with a rinpa motif, signed Fusayoshi saku.
Among other less likely candidates Haynes lists two Myochin Fusayoshi (H 00525,6) an Echizen man (H 00528) and a Yamashiro Fusayoshi, date of ca. 1590, H 00530. Given the workmanship the last one seems like the best fit, but without specific examples to refer to, who knows.
The head on view shows that not all of the holes are drilled perpendicular to the surface and that their radial locations wander a bit.
Viewed from the front, the holes have a larger diameter for the top quarter or so of their depth rather than being drilled straight through.
An angle view:
On the back there is no “step” visible inside the hole, but instead some eccentricity in the outline with a sort of lobe in places.
That irregular shape makes me think of finishing with an abrasive loaded string that was worked at a bit of an angle. I haven’t been able to find anything on early metal drilling in Japan, but there is a fair bit available on wood drills.
These were used by rubbing between the palms of the hands. Some of the above drills would produce a conical hole if only worked part way through, but looking at the Fusayoshi, the drilling looks more like a distinct step rather than a chamfer where the diameter changes.
Pump drills were used to speed up the process.
Pump drills were also fitted to a framework to create in effect a drill press. Presumably something like that was not used on the Fusayoshi given that some of the holes are drilled at off angles.
The care and technique that went into cutting the delicate openwork over this large guard is remarkable. I have to wonder whether the wandering placement of the holes was an aesthetic choice. Without magnification, the step in the diameter of the holes far from obvious so it’s hard to see that as being done for looks. The reason for that and the irregular exit holes on the back eludes me.
Not Japanese, but Clickspring has another great video on a possible process for making early metal drill bits:
The video on making a pump drill with a bronze spindle weight is also very interesting, but a bit farther afield from what appears to have been used in Japan.
So, back to tsuba – it is also interesting is that the rinpa has 30 points but there are 36 holes. The mismatch does add visual interest as the pattern goes in and out of phase. There are many significant numbers in Buddhism, but I haven’t found any special meaning to 30 and 36, although 5 and 6 have multiple meanings and are factors of those numbers. 108 is also meaningful, which is one tenth of 30*36, which is probably a coincidence… I’ll stop there.
When I came across this guard I knew that I had seen something similar before and had a feeling it might have been at the Dai Token Ichi. I still have some of those catalogs and found that it was not similar, but the same guard.
I balked at the Tokyo show price back in 2002. It’s hard to imagine that it was that long ago, but nice that it came around again.
Update: Looking through Toban Shokan Kotetsu I found a similar Fusayoshi saku tsuba. This book is a modern copy (likely copy of copies) of an early tsuba book from 1736. The tsuba are realistically drawn, not schematics. The thickness of the sukashi on other illustrated guards varies as you would expect in the real thing, so this one was presumably that finely cut in reality, which is rather similar to the above.
I don’t understand the meaning of yagosei before Fusayoshi saku. Literally it means 8 year old child. Yatsugo can mean octuplet, which doesn’t seem to apply here, with 6 design elements inside of a 7th. Yachitose (substituting te for ko) means 8,000 years, but stands for “eternity.” This is presumably a stand in that expresses something related but not literal.