Is My iPhone Factory Unlocked?

[Curleh Mustache]

Hey guys, A few months ago I recieved an iPhone 4 that is supposedly factory unlocked. I really want to update to the newest firmware but I'm afraid of potentially loosing the unlock. Can someone please tell me if my iPhone 4 is factory unlocked?

Here are the specs:
Version: 4.3.5 (8L1)
Carrier: Carrier 10.0
Model: MC318LL
Serial Number: 61131UZWA4s
Modem Firmware: 04.10.01

Note: I found a list of factory unlocked phones but a few people have told me that list isn't up to date.

Note 2: My Model is missing the (/A) at the end of it.