First console of the Game Boy line

Release date: April 21, 1989 (Japan)
CPU: 8-bit / 4.19 MHz Sharp processor (LR35902)
ROM: 256 kb, 512 kb, 1 Mb, 2 Mb, 4 Mb and 8 Mb cartridges
Display: 160×144 pixels, 2.6 inches (66mm) / Reflective STN LCD
Color palette: 2-bit (4 shades of “gray” {light to very dark olive green})
Dimensions: 90 mm (W) x 148 mm (H) x 32 mm (D) / 3.5″ x 5.8″ 1.3″
Battery: 6 V, 0.7 W (4 AA batteries provide ~15 hours)

More information @ wikipedia.org
Nintendo Game Boy Repair Manual @ ifixit.com