A tapered planchet exhibit a thinner edge on one side in comparison to the other. Therefore, a weight discrepancy would be expected since there was less of a planchet to begin with. If we judge by your images, then the coin will be thinner at 12:00 on the obverse and correspondingly at 6:00 on the reverse.
If there is no discernible thinness, then the planchet was originally underweight to begin with.
At least to my eyes, your coin appears to be slightly off-center.