I have to admit one of my biggest collecting disappointments was coin collecting. I thought it was a sure bet that coins would go up in value over time because of the limited editions of them. What I didn't count on was that with all the modern equipment very old coins would be recovered and bring down the prices of more modern old coins. Who is going to pay big money for a rare coin that is just a hundred years old when you can find ancient old coins that have been recovered for very reasonable prices?
I do think it's a good investment to save older silver coins that have a large amount of silver content just because the price of silver is likely to go up over time.
Here's a great site to find out what kind of treasures people are finding today.
http://pub69.ezboard.com/bancientlosttreasures