Sent from my SAMSUNG-SM-N900A using xda app-developers app
The AT&T version cannot be flashed right now due to a locked bootloader. Therefore it is impossible to have a custom ROM installed without it running Safestrap which you would see at bootup if it was as it would ask which ROM you wanted to boot with. The CUSTOM lock simply means you are rooted and nothing else. You do not have a special phone or anything.