What is the difference between these two heads?

I have 2 Santa C-3pos (sw0680) and one 2016 C-3po (sw0700). One has a shinier head, and while you'd assume it's the one that isn't a double, it was actually one of the Santas. I was in middle school at the time I got the second Santa from a friend and might have swapped heads around, or he might have. It is weird to me though that the heads of both the Santa and the 2016 figure are listed as the same on Bricklink, so it might be from an older C-3po It also looks like it's made from the...