Mine is a 1977 model, serial number #2309. Wozniak's Integer BASIC and a Revision 0 board (the full color palette isn't available for hi-res, no aux video pin, no "color-killer" for text mode). The switch on the power supply is a little testy so I usually have a Kensington System Saver fan attached, and one of the keys isn't as responsive as it should be, but otherwise it works perfectly! Not bad for a computer almost 30 years old!