These are two sizes of a puzzle box I designed and had printed by Shapeways.
It's a puzzle box that uses four US pennies as part of the locking mechanism.
To open, hold the box in one hand and quickly twist your wrist counter-clockwise. Or, set on a flat surface and spin the box in either direction.
Cool post. First time is see a puzzle like this.
Upvoted and resteemed. I used to have a puzzle stall in Covent Garden market... many many years ago.
!-=o0o=-!
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