The box doesn't say. Put a couple of different branded sim cards in it and see if they all work.
Alternatively, you could just check your unlock status with one of the many sites available.
Go to http://iphoneimei.info and enter the phones IMEI.
Apple should make it much easier to know that. Either on the phone itself or at least when you plug it into iTunes or perhaps someone on Apple's site.The box doesn't say. Put a couple of different branded sim cards in it and see if they all work.
Alternatively, you could just check your unlock status with one of the many sites available.
Keep in mind this isn't always reliable. A number of members have their unlocked iPhones showing as locked.
Apple should make it much easier to know that. Either on the phone itself or at least when you plug it into iTunes or perhaps someone on Apple's site.
If you buy an unlocked phone it will be unlocked. What else do you need to know?
I just picked up a white/silver 5s today but nothing on the box says it's unlocked. I was under the impression the box would say it's unlocked. If not, how would I know it's unlocked?
From previous experience, If you bought/picked up at an Apple store, it should say unlocked in the receipt, but nothing to indicate so in the box/phone itself.