I've come to the conclusion that the DX sculpt paint-up is different from the extra head I have. It's very subtle differences and you have to look hard because they're almost identical in colour and tone. But, the DX has slightly more class, if that makes sense? It has a few move liver spots (like the picture above) and the eyes are slightly better done. The extra sculpt hasn't been cleaned quite as well.
If I didn't know better, I still would've said they were by the same artist but he/she just picked the better finished/or later versions for the full figures.
Great pictures, everyone! :clap