Hello Niels, and Alexander
I am new to this forum and was interested in your thesis and interest in munechika.
I believe the only reliable source about Myochin ki Munechika ( it is the same reading as Munekane, but apparently when he was register as a resident in Edo, he insisted on being registered as Munechika) is his diary ( In Japanese).
Munechika was probably the last "official" armor maker of the bakufu, hence this official gift given to the Dutch king. Unfortunately, on the 2 armors that was given, the maidates are missing. The armors left Japan with the Maedate, and there is big chance they reach Holland but for some reasons were lost ( stolen?, storage? war?). That would be an interesting search if there is some document of this period left .
Munechika was a well know armor maker, and made armors for both bakufu officials, and individuals ( who could afford his work). His adoptive father and Munechika as well, had some students, and their work are very, (incredibly) similar. In Mr. Ishida book, you have a genealogy of this branch, and students.
When Munechika was called by the bakufu to work in Edo, he became extremely famous, and very wealthy. Munechika -'s armor was like having a Hermes bag. It was about status and prestige.
He had a workshop, and over the years, I was lucky enough to find 3 sets of his armors with the exact scale size, even the fabric used for 2 of them were identic. 2 of the armors are signed, and the other one ( leather) is not signed, but easy to tell, they were made using the same scales, and from the same workshop. Even the maidate come from the same clan. I do not know why this leather armor is not signed.( Made by one of his student? No sign on leather armors? )
Mr. Ishida who was a specialist of Myochin ( unfortunately passed away a couple years ago), asked Munechika descendant about any left documents from Munechika. They had a lot, but everything was destroyed during the Bombing of Tokyo during WW2.
What is left ( for now may be) is his diary, and studying his armors. Signature and date are usually found under the right arm. Some other Sangu parts can have a signature but not mandatory. If it is a full set, you should have the signs in the helmet ( with the date), the mask, and the cuirass ( right arm sign and dates)
For "tatami" armors, sign and date in the helmet, sign in the mask, and sign and date on the cuirass, but hidden under the back plate.
Of course as an armor maker, he also made some renewal work on damaged armors, made new armors using old helmet for example, etc. I saw an interesting helmet few years ago, but probably not his work. Only the shikoro was signed. Munechika probably only made the shikoro to match the helmet. Sometimes it was a collaborative work, where he did only one part of the armor.
Hope it helps. Good luck in your thesis. Would be very interested to read it when completed.
Kind regards