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We want to make the coins very affordable but generous in the amount they hold. What material can they be made from? --snip
Without any kind of reputation to back up your project, then is it not a good idea make coins that is prefunded with more and very small amount. It requires an enormous amount of trust in you, which you don't have, so your will have trouble selling your coins. My advice to you would be to sell them unfunded or below 0.05 BTC.