I believe the mint first used this type of packaging in 1994 with the Jefferson set. I can see where some of these were damaged by those trying to remove them from the packaging. It was not easy to free the coin. A few years later, Coin World and others started reporting the toning issue with these. Many were removed from the packaging for a quick dip and a better holder. It's cool that the OP's set turned out so pretty. Only 25,000 of the 1997 were made. Special coin for those building the Jefferson set.