I recently bought additional iPhone from China that was unlocked OTB.
Specs are as follows:
Firmware 1.1.1 (3A109a)
Baseband 04.02.13_G
Bootloader 4.6

Now I want to upgrade it to 1.1.3 via iTunes so I could unlock it with ZiPhone, but I want to be sure that it is safe and I don't brick it. The problem is that I have no idea how it was unlocked originally and I'm suspecting a HW unlock, cause there seems to be a very tiny dent between the plastic and metal on the backside from where all the HW unlock tutorials recommend to start to open the phone. But it also could be my vivid imagination

Fiew days ago I unlocked a 1.1.1 OTB ( jailbroken and unlocked) to 1.1.3 and successfully unlocked it with ZiPhone so I'm eager to do the same for this phone, but not knowing the unlock method scares me.
Anybody has an idea what unlock seems to be the most logical in this case? Or does it make a difference and I can just restore it to 1.1.3 via iTunes?