by meeotch » Thu Aug 19, 2010 12:21 am
When minifig torsos are printed, the arms haven't yet been attached. When printing on the torso's front, a black mark is added to the neck to identify the front. That way, after the part has been printed and it makes its way down the belt, if it gets flipped upside-down or anything, a photoelectric eye (or human who isn't intimately familiar with the design of that particular minifig, for that matter) can identify which side is the front so that the arms can be attached with the proper orientation.
"Always carefully check the source of your internet quotes" - Abraham Lincoln