Personally, I use the price of silver and gold to guide my numismatic purchases. If silver is down, go after a silver dollar like a Morgan or a Silver American Eagle (which are sensitive to silver price) for your 7070. If silver is up, go after that
Trade dollar which is pretty much immune to silver price. This is also a good time to pick up any common pre-1965 Mint sets you need. They won't go much lower even if silver drops. If I wanted to purchase more silver than that, I would be tempted to start a collection of
Roosevelt dimes,
Washington quarters, and
Franklin halves. I would buy the common ones when silver is down and the more difficult ones when silver is up.
Coinfrog is right. You don't want to start speculating in precious metals without any knowledge. Having said that, however, if I was going to add an album of
Franklin halves to my collection I would be tempted to buy a bag or half bag of junk silver halves and do the equivalent of coin roll hunting. Just get some '64 Kennedys to replace what you take and sell the bag back. That is, of course, assuming you would be satisfied with well circulated coins.
Gyrene is also right about
APMEX, but don't go to the link in our posts. That is automatically created by this message board and goes to their
ebay page. The prices are better on their web site. Just add .com after their name. That's where I have been picking up my pre-1933 gold pieces for my 7070.