SYM-1 by Ray Holt and Manny Lomas (after Microcomputer Associates they formed Synertek Systems).

Originally called VIM-1, this was a 6502 SBC meant to be a better KIM-1. The design shared the same application connector, so it was possible to produce expansions (the ASK family as Robert Tripp of The Computerist called it).
More I/O (6522’s and the 6532 for the same 6 7 segment LEDs and larger keypad), more RAM (4K), more empty ROM slots, a better monitor (vectored, so easy to interface to new hardware), optional Basic or Resident Assembler Editor.

On these pages a collection of available SYM-1 hardware and software.