I've read on the Washburn forums that Kasuga built Washburns as well as Matsumoku.
Having said that, I've just looked at the Daion Headhunter - Crusty, are you 100% certain Uncle Matt didn't build them - look at this:
http://www.diamondstrings.com/daion%20HH555%20HB-1.jpg
If Kasuga were building the Wing series as well as Matsumoku, then that might explain it, but otherwise I'd be convinced that was a Mat.
However, this being the wonderful world of vintage Japanese guitars, nothing is necessarily what it seems - so just to muddy the waters further, Frenchie should look at this thread:
http://www.matsumoku.org/ggboard/viewtopic.php?t=2896
To clarify, the Morris guitar in the dead pics in the first post was identical to my Hohner - and it would seem that neither of them were Matsumoku - they appear to be Wing-series
copies.
Jon.