Can somebody help me with this, the DSD both share the same COO, but the one on the left has a dent on his chest. 
I hope you can see it in the picture? Help anybody?

Assuming I'm not being a sucker to a joke post, what makes you feel that this isn't a BB gun shot or something?

It's a production defect inside the figure is a male & female socket which help align the two halves of the torso together. The plastic is naturally thicker in this area due to this feature, therefore different rates of cooling can sometimes distort the plastic. Hence a sunken indent. Hope this helps?