Sw-box has posted two videos which allegedly show the rear shells for the iPad 5 and Retina Display iPad mini 2.
It compares the dimensions and the weight of iPad 5 with that of iPad 4’s. The 239.20mm(H) x 169.5(W) x 7.2(D) new iPad proves to be slimmer, smaller and thinner than the 4th generation iPad. Comparisons are also made between specific features of the two Apple devices in question. It reveals their differences in speakers, volume buttons, the extra microphone hole, logos and holding feels. With the comparison, iPad 5 is likely similar to iPad Mini in appearance except size and the extra microphone hole.
These dimensions are close to the 240mm x 169.48mm x 7.5mm ones found in schematics being used by case manufacturers.
Take a look