Flame - if i remember correctly I believe Gayle previously mentioned it was a parts box, possibly for drill bits. Maybe check Walmart, Harbor Freight, Target, Ace Hardware, etc. I saw boxes with same-size slots in Army-Navy Store, made for bullet storage. I have utilized an almost transparent lidded box (clear with a slight white color), from Dollar Tree. That one was made for 3"x5" index cards. No dividers, just an open box. You can make dividers or place the box so everything remains upright. No matter what you utilize verify the number in a circle fits the range that has been tested OK for contact with polymer clay. Or line the interior with Patty-Paper.