For short term sorting and viewing purposes, a folding folder is okay. I like the Littleton albums with the sliding acetates, they will not tone the coins, and simply use care when opening (sliding the plastic protective covers). The brass holes for the 3 ring binders are very durable, in the Littleton albums! As the expert R. Cooper has said, some folks like toned (tarnished) coins some do not. I view most tarnish as true damage, and I avoid. Do not keep coins in any folding folder for long periods! Especially silver colored (CuNi) coins! Nickels will get a circular golden ring around the outer circumference, this signals that they have been in a Whitman folding folder too long. My world coins are kept in 2x2s, and then in "BCW" cardboard page which holds 12 2x2s per page. These are kept in large common 3 ring binders, in a Jumbo Hefty bag, with desiccants. I have posted images on another coin forum. If anybody is interested I can post them here too.