PHILADELPHIA (AP) — When it comes to making coins, the Mint isn’t getting its two cents worth. In some cases, it doesn’t even get half of that: A penny costs more than two cents to make and a nickel costs more than 10 cents.

Dick Peterson, the Mint’s acting director, says the problem is figuring out how to make coins more cheaply without sparing our change’s quality and durability, or altering its size and appearance.

A 400-page report presented last week to Congress outlines nearly two years of tests at the U.S. Mint in Philadelphia.

Evaluations of 29 different alloys concluded that none filled the bill. There’s more testing to be done in coming months.