I found the perfect size shadow boxes at Ikea to display my collection of antique salt and pepper shakers.
The boxes are uniformed in size and so, if I were to find a shaker that is bigger than the size of the box, I'd have to either pass on adding it to my collection, or find a bigger box.
The box is relatively inexpensive, costing about $6- each. I can either hang them up on the wall, or display them on a shelf.:D