I was curious enough to email the seller and ask... Apparently it was a "FoodSaver" bag.
FoodSaver: Apparently we can keep our notes fresh as well as our groceries. Add yourself a fancy looking card and voila!!! "Do-it-yourself" graded notes.
As stated on the site itself...."With FoodSaverâ„¢, you will extend the freshness of food, eliminate freezer burn, marinate meat and fish in minutes,
protect collectibles and other non-food items from aging and corrosion - and more!"
So does anyone else hide their notes in the freezer compartment?