Jeff Benjamin at the iDownload Blog thinks it is. Comparing it to the tiny box shot on the official Apple iPhone 5 ordering page, it looks legit, and also looks as if white iPhone 5s and black iPhone 5s will be shipping in vastly different boxes: all black for the black model, mostly white and light-toned for the white model:
Looks gorgeous. Can’t wait to rip open mine.
Source: iDownload Blog