Well i am sorry to tell you guys but i have seen this problem long before and i can assure you that IWC 3717 comes ONLY with silver center hands, there isn't and as far as i know wont be any version of 3717-01 made with black center hands.
As far as factories is concerned i can also tell you there are several factories making hands for IWC and you probably just got from a sloppy one. This being said i saw a set of hands with black center parts in the past and yes they seem to be good quality as well but for some reason they have painted the center pin, i guess its easier for them, not sure why it happen that way or if it was just a mistake.
This being said if you like them that's the important thing, you will have a custom one.
Ps: I find it funny modelizer that you say that getting a damage hand (or one from each color) is a faulty from factory and not from the one who supplied you the parts. i would never, ever ship something like that to any of the members that get them from me. And if i got them from factory like that, they would be shipped back straight away or i would take the cost myself.