A famous microprocessor devellopment kit: the KIM-1 (1978).
It's considered the 'granddaddy' of microprocessor systems.
Built around the MOS 6502 CPU (1 Mhz)
A 'whopping' 1024 bytes of RAM, and a HEX keypad.
Mine is neatly enclosed by a nice plexiglass box, and it now works as a clock!!
You could connect a Cassette tape recorder to save and restore the programs...
I still have the tapes!!!