I've carried my collection (approx. 6 kgs, silver, copper and few gold coins) from Calcutta to Goa via Bombay. The CRPF at both Calcutta and Bombay airports were curious, but they don't bother once I showed them the coins. So I confirm it is OK. I was lucky my hand baggage wasn't weighed, I'd have had to pay excess baggage.
I'd recommend putting the coins securely so they might not fall or you lose them since there can be long queues at security check points. I would not recommend putting them in the checked in baggage though.
Hope it helps,