Here is how I read the MSL/SPC on the Galaxy S3.
First make sure its stock unrooted. I have not tried it on a rooted device.
Lets get started:
Dial *#7284# and choose the last option. It should day DM+ADB+MTP I believe.
Then connect your phone and wait for the drivers to install etc...
Next dial ##3282# and choose edit.
Download the folder in the attachments.
Extract and open ADB
Then type: adb devices
Make sure you get a serial
Then type adb shell
Now go back to the S3 and when you chose edit it should ask for the MSL.
Type in 123456 you should get an error and when you do go back to Command prompt.
Then hit enter. You should get your MSL/SPC code.
If not then maybe your phone's AndOS is too new.
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