Help reading mei on a WWII bring-back wakizashi

[Updowncakes]

I'll preface this by saying this whole writeup was helped along by Claude, but all the measurements were done by me by hand, not some guesses based on pictures or anything like that. Also I think it put in way too much context, I am only looking for translation help first and then I'll go over to the other threads to settle the rest of the information about the sword, unless anyone is willing to help here.

Any and all help is greatly appreciated.

 

This came down through my family. My grandfather served in WWII and brought it home. The family account is that he was told it was surplus that had never seen combat. I have no documentation beyond that story.

I'm hoping for help reading the signature. I'm not asking for a valuation, and I understand the blade is out of polish — I'm not planning to touch it myself, and I haven't cleaned the nakago.

MEASUREMENTS (please tell me if I've measured any of these the wrong way)
- Nagasa: 55.2 cm / 21.75"
- Sori: 16 mm — measured as the straight-line gap from a taut string run tip to munemachi
- Kasane at base: 5.9 mm
- Motohaba at base: 27.9 mm
- Nakago length: 16.2 cm / 6-3/8"
- Mune: peaked, two facets
- Two mekugi-ana
- No stamps of any kind that I can find anywhere on the blade or nakago

What I can see, with the caveat that this is all AI-determined.
- There is a visible hamon. To my untrained eye it reads as irregular and wavy rather than straight, and something appears to continue up into the kissaki — but I'd rather have someone who knows tell me what it actually is than name it wrong myself.
- There is a yokote.
- The tsuba is iron, round, openwork. There is soft yellow metal packed into the nakago-ana, which I believe is sekigane.
- The habaki is brass with diagonal file marks.
- Someone has polished this at some point. There's cross-hatch scratching in the ji. I don't know when or by whom — it predates my having it.

THE MEI
Seven characters on one side, two on the other. Both faces are heavily corroded. I couldn't get a usable pencil rubbing, so I photographed the nakago and traced only the strokes I could confirm across multiple angles. Tracings are attached alongside the photos.

Seven-character side — my tentative read is 永 [?] 五 年 二 月 日. I'm reasonably comfortable with all of it except character 2.

Character 2 looks to me like it might carry a 廴 radical, which would give 延 — but as far as I can tell 永延 only ran 987–989, so there was no year 5 and that can't be right. Could it be 正 or 禄? Or something I haven't considered at all?

Two-character side — much less confident. The lower character might be 成. The upper one I can't call.

Full disclosure: those tentative kanji readings came from working through it with an AI, not from any expertise of my own. I'm flagging it so nobody treats them as informed guesses — please throw them out entirely if they're pointing the wrong way.

I'm putting many of these in an imgur album since I can only attach very small files here. Hopefully that's okay. 
Edit: Working Imgur gallery:
https://imgur.com/gallery/wakizashi-translation-help-J7XyTvA
1. Nakago, seven-character side
2. Nakago, two-character side
3. Tracing, seven-character side
4. Tracing, two-character side - this is actually the last image, had to re-upload.
5. Full blade
6. Hamon, close-up
7. Kissaki
8. Tsuba, face
9. Tsuba, showing the fill in the nakago-ana

Again thank you for any help you can provide.

Edited July 31 by Updowncakes

[YourBabyBjornBorg]

Hi! Sorry, every time I enter https://imgur.com/a/7nzxFej, it just sends me back to https://imgur.com/, so I can't see any of the pictures. 

[Updowncakes]

Sorry it's been quite a while since I've used Imgur! I should have checked it. This one should work:
https://imgur.com/gallery/wakizashi-translation-help-J7XyTvA

[YourBabyBjornBorg]

Sorry, it still says "the requested page could not be found", what am I doing wrong 

[The Blacksmith]

That new link doesn't work for me either I am afraid.

[Updowncakes]

It looks like sometimes it'll open for even me, sometimes it won't, and there's also a really big list of countries that outright block imgur now. Trying something else.
Sorry for all the issues.
Trying again on imgbb
https://ibb.co/album/n6Kd5b

[YourBabyBjornBorg]

Yes, finally! 永延三年二月日 Eien 3 (989), a day in February, 友成 Tomonari. Very, very Gimei (false signature), unfortunately.

 

This could be 永延五年 Eien 5, except there is no Eien 5, only 1 to 3.

 

The earliest genuine date on a Japanese sword is said to be 平治元年八月二日 August 2nd., 1159 (really it's September 16th, 1159. it's a whole thing, Japanese traditional calendar vs Julian calendar and stuff), on a Juyo Bijutsuhin ("Important Art Objects") Ko-Naminohira.

 

Ko-Bizen Tomonari is one of the most famous and well-regarded smiths of all time. I believe there are many information about him in English on the internet.

 

Also, the Habaki on your sword is quite nice, which is usually a good sign of a sword's potential quality. It's what we call, sometimes facetiously, appraisal by Habaki (鎺鑑定, Habaki Kantei).

 

 

It's very hard to see Hamon and Kitae in the current state of polishing.

 

 

This is O-Gunome ("Big Gunome", these continuous and almost semicircular shapes), very rare, maybe Mino school, but not sure about the time period. Could be from late Muromachi all the way to WWII.

 

The Yasurime (decorative file patterns on the tang) looks like Takanohane, which is also quite Mino.

[Updowncakes]

Awesome! Thank you so much! So, a faked name and date on it, but it's still a better story than my dad and grandfather thinking it was some mass-produced sword.

[YourBabyBjornBorg]

I can't make out the whole of Yasurime in one picture, so I have to piece it out.

 

 

 

Put the two together and it looks like Takanohane as shown below.

 

[Updowncakes]

That's so much more detail than I was even expecting. Thank you so much!