I don't have any gold coins in my collection, but I do have a fair amount of silver. Now with the older (pre-1965) silver coins, their collectors value is generally much higher than what would be the metals value. That being said, I've also been accumulating so-called bullion coins like the 1 troy ounce Sterling Silver (99.9% pure) American Eagle 'Dollars':

I've been buying 10 or so of these per year for the last several years. One coin goes into my collection, the remainder I hold for their investment value.
Note that while you can purchase so-called collectable or numismatic coins directly from the US Mint (which I do every year), you can only purchase bullion coins from what the Treasury Department refers to as 'Authorized Purchasers', such as coin dealers, investment brokers, precious metal firms, etc. These places generally offer the coins at prices based on the daily spot market.
I generally buy my bullion coins from APMEX which sells Silver Eagles at about $3 or so over spot, which today was $16.12/ounce.

OCU