Originally Posted by SacTilt
According to the description:
NFC is functional from mobile to mobile only or mobile to NFC Tag as well, depending on your needs choose appropriate model.
This tells me that the "NFC compatibility only" is for "mobile to mobile only" and "NFC Tag compatibility" is for "NFC Tag as well".
The difference in the two is that the one comes with the label on the receiver and the other already has it removed. My coworker ordered the mobile to mobile version and I ordered the NFC Tag version. Difference was just the label. Basically if you look back at some of the earlier threads, you will see that the aluminum foil is blocking the NFC from functioning properly. Thus it needs to be peeled off to all NFC to work. I believe fonesalesman is probably ordering these in bulk (as it has his branding on the lablel) and need to peel off the label manually to allow NFC to work, thus the extra cost to do it himself.
Also, the reason the NFC works with label for mobile to mobile is that you have NFC from both batteries / phones connecting / trying to work. Thus I bet there is just enough communication, along with the other phone, to allow NFC to work between them. Remember you have the phones back to back, so this is probably strong enough to work in this scenario with the label on.