I sold 2 iPhone 4s (4 not 4S) on CL tonight; a 16GB and a 32GB. The iPhone 4 has no capacity (16GB/32GB) etched on the back. (And even if it did, the back is easy to swap.) I had wiped them both, and thus the "connect to iTunes" message was on the lock screen. The only info available when the phone is in this state is the CCID and IMEI numbers, found by tapping the i on the lock screen. Fortunately for me (and the buyer), I had the original boxes, with matching CCID/IMEI numbers on the sticker on the box, and the corresponding capacities 16GB/32GB. So if you are buying a used iPhone 4 without the original box, and the phone is in "connect to iTunes" mode, you have no idea what you're buying. The only way around it I can figure is to bring a computer with you when buying, hook up the phone and check the capacity in iTunes.