Normally, Ilayaraja, I would say that a 0.17 gram weight discrepancy can be ignored. However, I am not so sure with a 1916 Calcutta, which is the KEY date of the series.
Key dates are always the targets of counterfeiters. So you must have your coin certified as authentic by PCGS, NGC, ANACS, or ICG.
If it is genuine, it is a $500 US dollar coin (or more).