No serial number would make me think that it is a Chinese knock off.
That said, a friend bought a few 2-7x33 knock offs for his grandkids' 10/22s and the last I head they were still holding their zero. A set and forget scope might do better than one that was intended to be regularly dialed for windage and elevation. A local pawn shop over-paid for a rifle a while back because it had a "Leupold" scope mounted that looked correct, but was actually just a well done Chinese knock off. They aren't buying or taking Leupold or Zeiss scopes in trade any longer because of the influx of Chinese knock offs of those 2 brands.
