Habaki were never soldered in place.  I've even seen an iron habaki;not
soldered in place.  Kinuki Gata tachi has habaki as integral part of the
blade or the habaki is fitted from the kissaki and is pinned into place. Again , not soldered

Most likely this habaki has been soldered in
place by someone state side and I have seen this more than once.  Seems that
the Habaki falling off or moving a bit is not acceptable to the G.I.
bringing it back and one solution to this "problem" is to soft solder it in
place. Another  scenario is that the habaki was not original and the solder
"sured up the fit" so to speak. Now it might be difficult to remember if the
peice was soft soldered or hard soldered onto the blade but I'll lay odds
that it was soft. Soft solder is very rarely found in Kodugu or other
Japanese metal work.  I'd like to say never but as the addage goes........
Please don't mistake the tobacco and menuki hat pins etc. we see on occasion
with soft solder schmootzed in the back as the norm.   This is "after
market" application.  I also treat any menuki post that is soft soldered as
a repair.  Soft solder, if skillfully done ,won't harm the patina of kinko.
Hard requires temps of 1200-1800 deg F and detroys the patina.  The peice
must be polished and repatinated to restore the color.
    I'm trying to write a small article on habaki construction, foundation
quality, and  its impact on the overall  balance of koshirae.  Remember that
the habakishi, though third in line to see a newly finished sword,  is the
first to apply materialy tangible outside influence.  His eye and work must
contribute to the beauty and balance of the sword .  His work will directly
affect the balance of all work that follows.  I hope it will answer some
questions that have arisen and might raise some new questions as well.

John