Military Coin Display Case: Mirror Back | Creative DIY display case ideas for inspiration. tag: #diy #displaycase #ideas #actionfigure #military #jewellery #food #. 12" x 15" 40 Coins US Flag Military Challenge Coin Display Case Military Promotion Retirement Gift Army Navy Air Force Marines Coast Guard. Handmade solid. Take the piece of wood that's 12 inches by 8 inches by 1 inch in size. Cut a piece of felt that is 2 inches larger on all sides. Apply glue to the felt. Draw further lines at the 4 inch mark and the 6 inch mark. Glue it in homemade coin display case as well. Wipe off any excess stain after five minutes and let the wood dry for two hours. Sandpaper Tack cloth A coin display case is something you will need if you have a large homemade coin display case collection. Also, sand the entire piece of wood with fine grit sandpaper before using a tack cloth to remove all the sawdust. Apply glue to the felt before folding it over the wooden piece so it is fully covered by the material.