Surfson

Please help us with the timing Paul.   What time will you be going and casting?  

Let me add my condolences to those expressed thus far.  I too am crushed by this ever so sad news.  He was a great student of nihonto, with unparalleled knowledge and analytical skills.  Along with others in our field, I will miss him greatly.  

No signs of an era that I can see.  No worries though, still an interesting blade and worthy of further study.  I would look into the Yoshimitsu mei if I were you.  

Especially some close up photos above the nakago ana on the side with the date.  I am curious as to whether the patch that appears to have been polished in some way may have remnants of an era in it.  

I think it's an interesting older piece, probably early to mid muromachi.  

I haven't studied the mei but my first inclination is that it is representing Tosa Yoshimitsu.  

I think that this may be a better sword than you initially thought, and certainly worthy of more study. 

I think that more photos are in order and it might be an interesting piece.  I don't think that the mei was added recently.  In such a case, there is usually red rust in the carving of the mei, and this tanto doesn't have that.  Having half a date is odd, but it would be nice to see the whole tang and the whole sword.  

Maybe nashiji

I would guess Shimada Sukemune.

It is an interesting, and very political, family.  I had an Okimasa made at that forge that also mentioned a major political figure/patron.  That is a very collectible sword George!  

Not a great photo, but my favorite Shoami in my collection.

This one is supposedly Awa Shoami

And another - Akita Shoami

Here's another.  

Supposedly Akita Shoami from my collection

I have picked up many great swords on ebay over the years.  It has pretty much dried up though in the last 4-5 years.  

You are correct Michael.  I was going to bid on it but my polisher didn't like the shape!

George, is he any relation to Tsukamoto Okimasa?   Okimasa was one of the most famous smiths of the early 20th century.  

I just went back and looked at the Tanobe sayagaki for my Norishige (also a discovery - it was a unloved sword at a show).  In it, he uses Yuhin nari, which is very exciting to me considering what Markus told you.  Thank you for the useful information!

That is interesting Georg.  Did he mention Tanobe San's use of "chin chin cho cho"?

I can see the nie in the boshi now that it has been pointed out.  Sometimes the hamon is dark rather than light/white depending on the photography or sometimes the last polish (especially when amateurs polish a sword you can get this inversion of dark and light).  

That's a relief!

Jean, you may be correct that it was a Saotome tsuba before it lost its plate...

That's an interesting sword Mark.  As to the boshi, it may indicate that the tip was once broken and the new boshi after reshaping of the kissaki comes close to running off of the blade.  

Very nice Georg.  Whenever Tanobe San puts the words masterpiece in the sayagaki, it is a very good thing!

Will, I think that your instincts are pretty good, and we have seen so many newbies come up with much worse than this.  

I do imagine it is 500 years old+.  It appears to have a ko-kissaki.  

The tsuba is in poor shape but has an Umetada vibe to it based on the hitsuana.  

It has a nice kurikata, indicating that it was probably in handachi mounts.  

Finally, it looks to me like it was covered in cosmoline, and has never been cleaned.  One of the lines that looks like a ware in the shingoi ji is probably old cosmoline.  Having all of this old cosmoline suggests that it may not have ever been in the hands of a collector.  

I'm not saying you should buy it because according to the seller it has a few ware.  However, I think that your interest in it was not unfounded.

What a find!  It gives me hope, as the only way I am likely to own a Kiyomaro is if I find it unrecognized.  Congratulations again.