This one only qualifies as 'unknown' as it doesn't appear in any of the catalogues and seems to pre-date the official launch of the Matsumoku Westone line in 1981, but I think it is definitely a Matsumoku guitar -  and an obvious ancestor of the Rainbow I.
and the logo is the same as on the early acoustics.

The label in the f-hole says it was made by Matsumoku Industrial Company Ltd, and the logo is the same as on the early acoustics.

The label also gives the model number as  A1511 and serial number as 7910033, which implies it was made in 1979 (Both numbers are handwritten). The serial on the neck plate does not correspond with the serial on the guitar, but the 'steel adjustable neck' inscription was common on Japanese guitars of the 1970s and the plate may have been outsourced.

Thanks to Chris Wilkie for the pictures and info