During the first spiderling attack the collar and chain vanishes from around Carter's neck and then reappears.
During the spider attack, Tars Tarkas shoots John Carter's chains, but they are shown as chains around his wrists, and in the next shot her had a chain on his neck.
A Craftsman logo is clearly visible on one of the items of hardware inside the power station on Mars.
As Tarkas' men try to break into the air pumping station a zipper is clearly visible in the back of a warrior's costume.
When John Carter fights Tars Tarkas in the pit, he gets Tars in a headlock that snaps the right tusk on the actor's mask.
As Tars, John, and the Princess approach the pumping station, you can see the neck part of Tars' mask riding above his clothes. It can be seen multiple times as the conversation switches back and forth. But once they arrive inside the station, his "skin" is once again tucked back under his clothes.