At first, this piggy bank appears impossible to open, with a dovetail joint on all four sides. In reality, this is a simple box with two parallel dovetails, spanning the same direction as the coin slot.

Print Instructions: Print both models with the z axis oriented the same as in the STL. No supports necessary. Slicing with 3 shells and a 0.4mm extrusion width will completely fill the walls and making it solid. The lid and bottom can be printed at the same time with any printer that has a similar build volume to the Ender 3.

*Update: The Bottom-Tall model is double the height of the original (140mm).