According to photos posted to Apple’s iPad Gallery, the Wi-Fi-only and Wi-Fi + 3G models use different back casings.
While the non-3G model features nothing but a black Apple logo and the normal model name, capacity, and other legal information on its back, the 3G model features a prominent black plastic strip occupying roughly two-thirds of the central top portion of the back casing, which is consistent with details provided to iLounge prior to the device’s unveiling.
A photo illustrating the differences appears below.
