Expert: Dmitry Livshits - 9/12/2010

Question
Hi, I have a collection of coins from the British Empire, particularly British India. I have recently starting weighing my coins to check their authenticity. I know, for example, that the one rupee coin should weigh 11.66 grams. Some coins weigh the correct amount, give or take a fractional difference. However with some the difference is a little larger, for example, 11.55 or 11.5 grams. I even have some that weigh 11.3 or 11.2 grams.  I was wondering if each and every one rupee coin should weigh 11.66 grams exactly or if it is normal to find some variance in the weight? Would you expect coins weighing 11.55 grams, for example, or less to be fakes?

Thank you in advance for your help

Answer
Hi Ian,
It is perfectly normal to find a bit of variation in these early and fairly crudely made coins. The coins that are lighter - are they particularly worn? Or do they have "test punches" in the surface? Test punches were used in the past to assay the silver content. Either of these would cause the lower weights you mentioned.
The fact that you did not report any that are heavier than reference weight is a good sign that your coins are genuine.
Coins would have been weighed after minting, and any excess weight would be filed off (what many people refer to as adjustment marks on a coin).
I do not have my reference books near me at the moment, but if I recall correctly some of the Indian mints normally issued 11.55 gram rupees.
My experience with Indian rupees of this period is that the fakes are significantly lower, as low as 7 grams and generally not above 10.5. The few lead-based fakes I've seen were heavier by .5 to as much as 2 grams.
Thanks for the question! =)