Floppy disk controller board. WD171773 controller chip. Socketed 28 pin Extended Color Basic 2.1 chip. Every edge connector pin has a toroid choke. Metal shield on the board's back side. Hole in the center for case bolt. Made in Korea. Works fine with Coco-3. Photos: http://qdv.pw/eng/_photos/Computers/Coco/cartridges/FD%20controller-no%20case/ Kandur