This is a piggy bank, made to look like a pirate chest. It's quite small (10cm by 6), can be used by our kids to hide treasure or their first coins.
Loosely reworked from linked design, started from scratch but took quite a bit of inspiration. Designed entirely in inkscape, looking at the different slides might provide some additional idea on how it's been done.
Cut out of 3mm thick material (I used plywood, MDF should be fine)
Red is for cutting
Blue is engraving (license)
Green is motif engraving
Pink is indication, don't print :-)
Box is a trivial assembly: use glue, snap in place with a rubber hammer and use a press to hold tight
Lid is a non trivial: link the arch (1) and the L-shaped piece (2) together (twice).
Assemble the lateral planks (3 - it should be a tight fit) then the top one (4)
Then slide both sides (5) in place. Soft hammering might be required.
Additional instructions (step by step photo) and explanations can be found on my blog http://www.revelut.ch/2015/06/04/piggy-bank-for-kids/