According to 9to5Mac’s Mark Gurman:
Apple today released an unlocked GSM version of the iPhone 5s on its online store for the United States. This version of the iPhone 5s includes the same exact capabilities of the non-unlocked models, but does not include a SIM card. Users who buy this version of the iPhone will need to supply their own SIM card.
The central benefit of an unlocked iPhone is that it can work on many GSM networks across the globe with no contract. For frequent world travelers, this option is worth looking into.
And Apple:
If you buy iPhone for T-Mobile, it will arrive with a nano-SIM card already installed that you can activate by visiting an Apple Retail Store or a T-Mobile store or by calling T-Mobile. If you buy a SIM-free iPhone, you will need to purchase a GSM-compatible nano-SIM card separately.
In the United States, you can purchase such a SIM from AT&T or T-Mobile. When you travel internationally, you can use a nano-SIM card for iPhone 5s from a local GSM carrier. The unlocked iPhone 5s model is A1533 (GSM). For details on LTE support, see here.
The SIM-free version of iPhone 5s is going to ship in 1-2 weeks while T-Mobile models will take 3-5 days according to the online store. The GSM device from T-Mobile will only work on GSM carriers and T-Mobile and AT&T, but not on CDMA network as that of version.
It is also expected that iPhone 5s unlocked version comes to the stores soon especially before next week.
