Designed and sold by Wichit Sirichote. Full text and files at his website here. The kit is available for sale, kit or assembled!
Wichit picked the Z80 CPU and designed the microcomputer kit with HEX keys and 7-segment LED displays, and wrote the monitor program.

The 6809 microprocessor kit is a member of the microprocessor kit family (I have also the 6502 and Z80 kit), and share a common design as far as keyboard and LED display and 32K RAM concern, in a format comparable with the Microprofessor 1b.
This kit has hardware serial (68B50) UART at 19200 baud, a big step up from the software serial bit banged slow 2400 baud in the other kits.