Just some thoughts.
These are super cute. The designs are great and they aren't a hard build.
For anyone making them some somethings I found useful. Use card-stock for the inner pull mechanism, or consider reinforcing it with at least a line of tape from one end of the pull tab to the other, on the underside.
Next, if you use cardstock you can make a small adjustment before gluing on covers. Take a straight piece of cardstock and afix one flush with the underside of the unlock slit. Then test where the slider will rest when closed and afix a peice to the tab underside flush with the first piece of card-stock. I found it useful to make a more solid catch.
Lastly for the arcane make, when finished if you don't like the look of the locked tab obscuring things you can curl it backward and tuck it under the slit made for the tray, and find a place to crease it to your liking. (Leave room to get a nail under it or enough room to pull it free.) Then carefully trim the other side so it doesn't obscure the roman numerals.