iirc it's satoshi but some subtle mining behaviour changed, particularly the nonces.  Early satoshi's mining software had used one particular method to pick nonces, but at one point in time the distribution of chosen nonces changed significantly and it seems as though another person was mining to satoshi's addresses (or satoshi changed the software used to choose nonces). Anyway, we can't know if all of satoshi's bitcoin were mined by the same person, or if it changed at one point in time and someone else carried on under his name.