Ray Holt also went on to design the Jolt computer, a very early 6502 based computer which lead to the SYM-1 (also designed by Ray Holt), and TIM-1, which was more of a kit with a pre-programmed ROM. I built my own TIM-1 this year and have been doing a bit of research into these early 6502 boards. The Jolt computer is perhaps most famous for being used as the microprocessor section in the first Atari 2600 prototypes.