Screw Top D20 Dice Box with detachable carrying strap.

thingiverse

This is a large (160mm) dice box shaped like a D20 with a screw top lid, and a recess to house a magnet in the underside of the lid for attachments.The idea behind it was a strap with a magnet attached would make carrying the rather large box to D&D sessions easier. Technically you could also attach other things to the top like a dice tray or a miniature.