The Mike 2 was a bare-bones system–just the CPU board with a 20-key keypad and a seven-digit display. The customer supplied his own cabinet and power supply. The system was upgradeable to the faster 8080-based Mike 303A. The Mike series was for hobbyists looking for an inexpensive entry-level system.
Reader GR Duggleby adds this:
Martin Research Mike 203A (Mike 2)/Mike 303A (Mike 3) (1975, computer trainer)
Original Retail Price: $270 kit (Mike 2)/$395 kit, $495 assembled (Mike 3)
Base Configuration: 8008 (Mike 2)/8080 (Mike 3) CPU, up to 4K RAM, PROM storage, seven-digit LED, hex keypad, monitor software, operation manual
Important Options: I/O interface
Martin Research Mike 8 (1977, computer trainer)
Original Retail Price: $895
Base Configuration: Z80 CPU, 4K RAM, 1K ROM, LED readout, integral hex keypad, EROM programmer, power supply