Just read that too though I mailed the owner a few days ago asking if it was unlocked.
This is the reply I got.
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Good afternoon,
I contacted Sprint in regards for international use, and they have provided me with a master unlock code.
Now since Sprint does not do any of the unlocking, they have advised me to provide this code to you to present to the carrier that you would like to have service with.
The device is no longer tied to any account, and is free for use on any international carrier.
The provided master unlock code is xxxxxxxxx.
I have made sure of this before printing shipping label.
Of course nobody wants something that is of no use to them,
I am shipping now, and you should receive shipping information shortly.
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What would be the point in them unlocking a phone that has no Sim card slot? It would be impossible would it not?
Its CDMA EVDO Rev. A 800/1900
In the page you linked it says:
The iPhone 4 (CDMA/Verizon/Sprint) is similar to the previously introduced
iPhone 4,
apart from support for CDMA (EV-DO Rev. A, 800 MHz, 1900 MHz) rather than GSM. Although, it also has no SIM card slot, a revised antenna and button placement and support for a new 3G "Personal Hotspot" capability that makes it possible to use the iPhone to connect up to five Wi-Fi enabled devices.
Notice the highlighted part. Maybe I will be ok no?