The model number on the back cover is:
A1349 on the iPhone 4 (CDMA model)
A1332 on the iPhone 4 (GSM model)
◾The front and back surfaces are flat and made of glass.
◾There is a stainless steel band around the edges.
◾The volume up and down buttons are marked with a "+" and "-" sign.
◾The GSM model has a SIM tray on the right side that holds a "third form factor" (3FF) micro-SIM card.
◾The CDMA model does not have a SIM tray