For what it's worth, I don't think it's a Matsumoku - Mats tend to have some quite specific details that make them recognisable - usually the "Steel Adjustable" type neckplate & truss rod cover shape.
Neither are present on this guitar but what it does have is interesting. The shield-shaped neckplate pops up from time to time on 60s & very early 70s guitars, and hasn't as yet been pinned down to a specific manufacturer, although it's been associated with Fujigen - as has the unusual 2-ply truss rod cover. These appear on some late 60s Ibanez semis - like this model 1910 from 1969:
http://www.break-even.org/six2/guitarpi ... red-la.jpg
Ibanez guitars from this era are believed to be from Fujigen, and it's not unreasonable to assume the one we're talking about is from the same place, based on the similarities. As always, it's a circumstantial similarity meaning it's more an idea than an ID, but we don't have a lot else to go on as yet.
It's an interesting question about different factories making different parts - and that was certainly the case. It's very hard to be specific because there is no record of early Japanese guitar manufacture but you might find some identifying branding on components.
There are a few known outside sources for hardware & electronics - Maxon supplied a lot of pickups, Gotoh (spelled Goto on early examples) made tuners, bridges & pickups etc, & Chu Sin/Chushin was apparently originally a light-engineering company which supplied hardware, before moving into manufacturing entire instruments. These brands sometimes appear on components but unfortunately more often than not they are unbranded.
It's incredibly common to find identical parts on Japanese guitars from numerous different factories - this is one of the factors that can make identifying some guitars so frustrating. To complicate it even further, it also appears that necks & bodies didn't always come from the same factory, particularly on the early instruments.
Jon.