This is a totally printable gumball machine that accepts real quarters and rejects other coins. It is also designed in a way that once locked with a padlock at the back it can not be opened or any parts disassembled. The back hatch secures the money and access to the coin mechanism's locking pins. The collar around the jar keeps the jar from being removed. The hole on the top will take a preserving lid ring for a standard "medium" Mason jar. Or you can go totally legit and print the provided jar file.
This object is an example of the mechanical application possibilities of a 3D printer. However the mechanism isn't completely reliable and with the cost of the print being over $100.00 it would be more practical to buy a metal one. This object is really just proof of concept but it's still really cool.