http://www.stltoday.com/stltoday/news/stories.nsf/nation/story/04B380EC65E89D398625740A000D4F50?OpenDocument
Sorry, I don't understand the joke. In the last few days of WWII Japan did have baked clay 1, 5 and 10 sen, but so far as I know they have never had plastic coins.
Its not actully plastic, thats why I said it was a joke. But the 1 yen coin is very very light. I'm not sure what its made out of, but everytime I see one, it reminds me of like one of those fake dimes that would come in a money set used to teach children about money.
The Japanese 1 yen coin is made to be exactly 1.0gram which is neat as many children around Japan still use it for scaling purpose for various experiments.
Aluminum costs more than zinc per pound, but I don't know if it would bring the cost of a penny down to under 1¢ due to it's low density. Now here is another alternative. For 20+ years, there are companies that have perfected techniques for electroplating copper onto plastic and other non-metalic materials. They could start using a durable polymer and copper plate it so it looks the same as a penny. Of course now it would be more like making buttons than it would be like making coins.
Because of the low density of aluminum, the same weight of metal has 2.64 times as much volume, so you could make 2.64 times as many coins with the same wight of metal. You can make about 180 cents with a pound of zinc $1.16 per pound, metal cost .6 cents per coin), or 479 cents with a pound of aluminum ($1.39 per pound or metal cost of .3 cents per coin). So even at the higher cost per pound, the materail cost per coin is 50% less. Steel weighs about the same as zinc, so in order to get the cost per coin down the cost of the metal has to be less than that of zinc. I don't know what steel costs. Figure I found for steel plate is around 46 cents per pound. That might give you a figure of .25 cents per coin.
