u probably got the copy...not original.
download battery bar or some similar software and see how many mW-hrs capacity it is. If its same as original, good. else its a "copy" (nothing there to copy, they just put lesser/smaller cells in there).
Also @OP , you can try and cut open your original battery and see what kind of cells are in there. If you can find those same kind of cells in market for cheap, just put those in and you have a DIY battery...I'm gonna try this once my battery completely dies out.