for Foster / Fostex

Foster / Fostex are two brands that came from the same factory. The brand names and model numbers of the two brands are used interchangeably, it is possible that your tweeter says Foster, while at the same tweeter in different cabinet has the brand Fostex.
The speakers of these brands were used by many speaker builders. Famous brands include Carvin, Mackie, PAS, Roland, Peavey, Sonic, Tapco, Yamaha, Yorkville etc. These brands used full Foster / Fostex units in their cabinets.
At this moment Foster seems to have disappeared, the brand Fostex still exists only now focuses on other products.