I saw this divot on the hub and was wondering if it was used for anything

 

Used to align the stuff you are bolting to it?

 

hmmm I looked at some aftermarket ones and none of them seem to have it, if I had to guess I'd says it's used in the factory for alignment/installation

 

I saw that dimple on mine the last time i replaced my water pump. it matched the pulleys that come off of it. Its probably not important enough for the aftermarket to do the same. If i remember correctly, the pulley seemed to only fit a certain way anyways. Those bolts are not evenly spaced. At least they weren't on mine.

 

ok so it might be a factory marking for the hole pattern, got it, makes sense