Compatibility lightning jack adapter

Hi all,

I just bought a lightning jack adapter. On the internet it says that its compatible with different kinds of Iphones. I have an Iphone 6 but this adapter does not work. Also by my friend who has an iphone 6 it doesn't work. I found on the internet that it should be compatible with the Iphone 6 (first generation). So not with other Iphone 6 models. How can I check if I have a first generation model? The adapter works works by the way (I checked). Thanks in advance for any help, much appreciated.