40% Silver Half Dollars, 35% silver war nickels, and standard nickels.

Each of these will hold legal tender value if all asset classes fail. If deflation happens a half dollar will always be a half dollar and a nickel will always be a nickel but if the value of the dollar goes screaming up in deflation then you may be able to purchase a loaf of bread with a nickel or a gallon of gas with a half dollar.

If inflation happens these go up in value based on metal content.

Note that this works for any junk silver coin with a face that is still in circulation but the cost is higher for the 90% silver coins.