It's actually kind like a display case...it has a glass top on it.. I have been wanting one of these for a while..it's nearly perfect for me. IDK if cardboard will hurt the coins..... anyone know if it will? stainless
as long as the coin is not sitting directly on the cardboard, and instead some other, safer, material.. you should be fine. One never knows where cardboard was prior to being used as a side project, so one never knows what might be lurkin in its fibers.