Hi Simon,
I totally agree with you regarding Yasukuni swords, they evoke the spirit of the old Samurai ethos. They were swords made for utilitarian purposes as well as art, the symbolism perhaps exceeds the workmanship but nonetheless an important group and that how I feel these swords are valued. Of course this does not include several excellent masterpieces but these were the exception not the average stuff.
Many famous early Showa smiths made average swords for the military effort, many were daisaku dai mei, many had copper habakis. They have to do this on one hand to reduce cost and by contributing to the army they are allowed tamahagane in return. Many average smiths made on the occassion a masterpiece that outshown swords by more famous smiths, these often were special order and fitted with higher quality habaki often silver. Gassan Sadakatsu make their own habaki and they too have copper, silver, gold foil and pretty sure solid gold habakis too.
I enclose a picture of a Yasukuni naval tanto, the habaki is a silver one which looks like those on other high quality swords in gunto mount.