My work gave me a white iPhone 4S and I don't know how many people had it before me. My personal phone is a black iPhone 4S. On the white phone, the front glass has a lip all the way around the edge. If I run my fingernail down the screen I can feel it catch on the very slightly raised lip before it gets to the edge. On the black phone there is no lip and my fingernail slides right off the edge of the glass without catching. If anything it has a slight bevel or dropoff rather than a raised edge. Is that normal? Could it be a difference in part suppliers? Did Apple make a change somewhere during the production life? Or could I possible have an aftermarket glass that got installed somewhere along the way?