Gold coin of 1912 issued by British rulers. whats its value today?

Question

I have a gold coin weighing 8gm issued in those days as pay to indians during the british rule . (given to my grand father) . The coin has the empress head on one side with the year printed therein.

Answer 1

The coin you are describing sounds - by size and weight - to be what was called a sovereign.
http://www.thegoldcoinstore.com/WorldGold/British_Gold_Sovereign_Canada_Mint.php

These were minted throughout the old Empire.

But 1912 sovereigns had the bust of George V, and not an "empress" (presumably Victoria?)

If it is a sovereign, it's current retail value would be approximately 90-100 British pounds, depending on condition:
http://www.24carat.co.uk/goldsovereignstocklistdatesframe.html

If it is something else, it might have more value as a collector's item.

Answer 2

It sounds like what you have is a British Sovereign coin (exact weight is 7.8 grams of 22 carat gold). These were minted in several British colonies, including India and South Africa. The mint mark is located on the center of the mound underneath the horse's hooves (I'm assuming that your coin is the 'St. George slaying the Dragon' type.) The ones minted in London have no mint mark.

This type coin sells for abaout 10% over the value of the gold in the coin. For more information, check eBay. There are several coins of that type for sale at any given time.