ID Your iPhone
Do you know if your phone was originally sold for use with specific carrier or for a network outside the US? If not, parts other than logic boards of these models are interchangeable.
I have GSM model for AT&T or T-Mobile in the US; Bell, Rogers, Telus, and affiliate brands in Canada; or Telcel in Mexico.
I have a CDMA model for the US market Verizon network.