Founded in 1964, they are also called San~tsuha instrument Co. and sometimes go under Mituba Gakki, (without the s in the middle - maybe translators?) They are based in Maebashi, Gunma Prefecture Japan and they currently make furniture and a brand of Ukuleles they call Zephyr. I have only ever seen Soprano scale on sale apart from the type 30 that appears longer, (maybe Concert maybe just Supersoprano?), but I have seen longer scales and a Taropatch in an office at the factory. Zephyrs are reputedly fairly low end and they are distributed by Kiwaya. They also make some of the lower end Famous branded Ukuleles for Kiwaya, (I have seen some Famous Ukuleles with sound hole labels saying made by San~tsuha and some better ones saying made by Kiwaya). They also make Domo Ukuleles, a promotional brand based on a popular Japanese cartoon character. 

In the past they made Clover branded Ukuleles, some of which were exported and this is the firm that actually made the Canadian Northern ukuleles so they may have used other brand names, or made instruments for other people too, (I know they did for Barnes & Mullins in the UK)?