If you are referring to a software unlock it's my understanding that those died a few years ago.Just asking.
You might try one of those R-SIM which allows you to use any SIM.
There is no sim interposer compatible with baseband newer than 4.10.xx
It worked on my iPhone 5C with R-SIM 9 PRO. I am able to use any network. There's also one for iPhone 4.
R-SIM 9 PRO is for 4S and newer.
I personally have never seen any sim interposer to unlock iPhone 4 with 4.12.xx baseband.
Lol you're right, my bad I thought it was for iPhone 4 to 5S![]()