Year introduced: 2010 (GSM), 2011 (CDMA)
Capacity: 8, 16, 32 GB
Colours: black and white
Model number on the back cover: A1349, A1332
 
Details: the front and back are flat and made of glass, and there's a stainless steel band around the edges. The volume up and down buttons are marked with a "+" and "-" sign. There's a SIM tray on the right-hand side that holds a "third form factor" (3FF) micro-SIM card. The CDMA model has no SIM tray.
See the tech specs for iPhone 4.