Medallion inserts for my trading card shelves that I have up on the store. Feel free to modify these medallions as you see fit. As long as the dimensions are the same on the outside of the model, the medallions will fit in my shelves. You could also maybe put certain symbols on the medallions to help organize shelves by color, but I will leave this as an exercise for the maker.

Link to my shelf model: https://www.printables.com/model/706012-trading-card-modular-shelves