metal punch cards, stored in low acid clay vessels in a very dry place. Seems to have worked so far... http://en.wikipedia.org/wiki/Copper_Scroll http://en.wik

metal punch cards, stored in low acid clay vessels in a very dry place. Seems to have worked so far... http://en.wikipedia.org/wiki/Copper_Scroll http://en.wikipedia.org/wiki/Copper_Scroll