I have an iPhone 4 black 32 gb with iOS 4.3.3 model

No. It would work with any SIM if it was unlocked by hacking or jailbreaking it. The only way to be sure it is factory unlocked is if you bought it directly from Apple and the receipt says it is unlocked, or if you bought it from a carrier and they unlocked it for you. If it was unlocked by hacking or jailbreaking then upgrading it will lock it to the original carrier in the best case, or permanently break the phone in the worst case.

I bought it from an independent store which they sell unlocked iPhone as they said. Not directly from Apple 

The term "factory unlocked" has no meaning. iPhones are sold either locked, or unlocked. If they are locked, ONLY the carrier it is locked to can authorize unlocking it, which is done via iTunes. If any other method was used to unlock it, it is hacked and will probably become a brick if you update or restore it.

Lysander2008 wrote:

I bought it from an independent store which they sell unlocked iPhone as they said. Not directly from Apple 

It's hacked.

I have the model number MC605ZP which is in the list of unlocked iPhones. Will this an assurance that it is really factory unlocked?