GSM vs CDMA iPhone 4

Well, I know that this will come as a surprise to most of you, but today I just learned of another difference between the gsm and cdma iPhones. See I had just recently done my first repair on a gsm model. Lo and behold, the back cover from a cdma model did not fit the gsm model. So, I ordered up one specifically for a gsm model and guess what-- it fit.

Like I have said all along, even though no one believes me, to date the only thing I can find out which will interchange between gsm and cdma models of an iPhone 4 is the battery. There appears to be nothing else in common between these two models. And if anyone has any experience with this, I would greatly welcome their comments here.