Since I am a hobby jeweler, I do not purchase a lot of metal sheet. However, I do have at least one or two 6"x 6" sheets of a variety of sizes that I use often. A 6"x 6" sheet fits in many sandwich bags and each gauge gets its' own bag. To keep the cut metal sheets from possibly scratching a pristine one, put a piece of thick acid free mixed media paper or thick scrapbook paper between them in the bag. A strip of anti-tarnish paper is slipped into the bag as well. The bags of sheet metal can still get jostled around in storage and scratched or dented, so maybe my storage solution can work for you. Each bag is labeled with the type of metal and gauge it contains. Inside the bag, every piece of metal, no matter the size, is labeled with the gauge. After using a piece of sheet and before all the unused pieces are put back in the bag, they are labeled with the gauge, a good habit to get into. There is no guesswork needed when an orphan piece is found, because it was already labeled. Smaller pieces are put in a separate labeled bag inside the larger bag.