A wooden nickel stored in a plasticized PVC flip runs the risk of having some of the ink dissolved and transferred to the surface of the flip.
Polyester (e.g., Mylar) flips are recommended as enclosures. These can, in turn, be stored in archival quality 35-millimeter slide sheets made from either polyethylene or polypropylene.
The slide sheets can be then placed in a three-ring binder or an archival quality box. If your collection is not handled often and you do not wish to incur the cost of flips, the nickels can be put directly into the slide sheets.
All wood is inherently acidic. As such, I recommend storing your wooden nickel collection away from acid-sensitive items such as coins and paper money.
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