Yonezawa is founded in the 1950's and was one of the largest and most creative of all (post-war) Japanese tin toy producers. Some of these toys were marked STS instead of Yonezawa. The origin of this STS label remains unclear, but it could be a toy importer.
Yonezawa shortly dabbled in RC toys in the mid-1980s with the Wave Hunter buggy (scale 1/10), in North America known as the Monogram Lightning.
It is uncertain what has become of Yonezawa, but some believe it is involved in the manufacturing of (industrial) electronics.
Yonezawa was a large toy maker, producing thousands of different mechanical (friction, clockwork, etc.) but also battery operated toys in all sorts of categories from the 1950's through the early 1970's.