This past Christmas, I needed a present for a picky friend that is really into vintage thingss. The idea I came up with was to recreate the style of bank vault that my late grandfather used to make. They use 'small' 5" x 3 5/8" sized doors commonly made by Corbin or Ranco (usually $10-20 on ebay or Etsy depending on style and quality). Additionally, you will need (4) 1/2in screws and (4) 1 1/2in screws for construction.
The filament I used was Hatchbox wood with 20% infill and 4 thickness on walls, ceilings and floors for structural integrity.
All 5 pieces print flat, so no supports!
After printing care includes sanding and staining. The recomended construction of the box is to glue between the finger joints. You could glue the back piece but I recomend using only (4) 1.5" screws to hold on the back (incase the lock malfunctions or you forget the combo.