SInce the largest coin marketplace in the U.S. is eBay, you can do your research there.
1. Go to the eBay front page, and at the far right, click on the word “Advanced"
2. Type in the terms you see on each coin (India Rupee 1903 for example) in the “Enter keywords” box.
3. Scroll down to the box for Category, and select “Coins and Paper Money”
4. MOST IMPORTANT OF ALL, scroll down to “Search Including” and click on the button “Sold Items.”
5. Click on the button “Search” and you will see a list of items like yours that have sold recently, and their selling price.
For example, with the term India Rupee 1903, you will get about 15 results on recent sales. You can pick the ones in similar condition to yours, and get the answer.