Investments to me are a three headed beast very generally. Stocks, Real Estate, and Commodities. Stocks currently are over-inflated and over-manipulated, plus people are extremely gun-shy after 9/11 and Enron et al. Real Estate is presently over-priced due to greenback flight from the stock market and self-styled Real Estate moguls, save your positioning for bargains in the next 18 monthes. Gold, not petroleum, is the ultimate hedge in the commodity market and, IMHO, grossly under-priced. Even if I am wrong, it is highly unlikely that you would lose money investing in Gold. In a worst case social collapse scenario you have excellent bullet making material, and a base medium of exchange.
Collector prices depend upon the opinion of collectors as to rarity, desirability, marketability, and condition. New coinage or bullion may be the way to go if you desire inflation and crisis protection. Consider denominations smaller than one ounce for practicality in some scenarios. Stay away from gold manufacturing and mining stocks. It is an incredibly dirty process to produce gold as cheaply as possible and environmentalists are rearing their heads in that direction. As an aside, the same goes for aluminum, and, as far as I know, silver.
This is not my area of expertise, but my semi-learned opinion. Properly proportion your investment portfolio.