2013 Purple 2 Dollar Coins Available in Bags of Five

[Fulvio]

They have many bagmarks and black tone spots already.

Yup. No special care whatsoever was taken.

One thing I've been considering to stop further degradation...

A friend of mine found a cheap commercial vacuum pump on ebay many years ago, and attached a hypodermic needle on the end of some plastic tubing. He seals up delicate electronics, inserts the needle, sucks the air out, then tapes over the tiny hole.

With these bags, that would stop both the coins moving around and bagging further, and any aerobic chemical reactions. Just a thought.