I recently came across this guard online. It was impossible to make everything out from the photos, but it looked like there were two different hands at work. After some rust removal we have the following.


So, even without reading it, it’s pretty clear that two different people signed.
The easier one first, the back, says Okamoto on the right and Yoshikiyo on the left. Okamoto is a family name found among a number of groups, and very frequently in Choshu. I don’t see a Yoshikiyo with these kanji listed, but Haynes 11517 is a Yoshiharu with the same yoshi, the family name Okamaoto from Choshu, so perhaps a connection.
H 11742 is a Myochin Yoshikiyo with the same characters working in Hizen. Normally that would be a clearly different guy, but given the other side I wonder if there is some connection.
So, the front – the left side is Myochin ki Mune… something. It’s an odd character and partially punched into oblivion. Going through the various Myochin Mune possibilities we find that the last Munesuke signed with that distinctive “xx” shaped suke. He’s recorded in Haynes at 06239 and Bob has handwritten the variant kanji in the listing.
The right side looks like hard work, but it’s convenient to know that it’s something that a number of Myochin smiths added to their work. Haynes reads it shinto go tetsu neru – “forged from five layers of iron.”
A few days ago I was reading Markus Sesko’s blog and found an interesting article on just this phrase:
About shintô-gotetsu inscriptions on Myôchin works
Markus reads it shinto go tetsu ren and suggests that rather than the standard interpretation the meaning may actually be “forged from an old begging bowl” of the type used by mendicant monks. Please read his post for the details and much more information. It’s very interesting.
So, a view of the entire guard with its carving of clouds:

The carving resembles Choshu work and given that Munesuke claims credit for forging the plate with either meaning intended, it seems likely that Yoshikiyo worked the chisels. His unlisted status may be because he wasn’t known for making tsuba on his own. Or maybe he is known as the Myochin Yoshikiyo and for some reason at this point was referencing where he came from.
I will have to ask some Choshu tsuba collectors if this apparent collaborative work is a well known thing. I don’t recall seeing it before, but this is outside my usual area and I may have some or all of it wrong.
Update: Not a known thing so far.