These can be used to collect ballots, coins, and/or bills. The are secure because you must destroy the can to get the valuables out, so you'll know when the bank has been raided.
And they're reusable. When it's time to collect, just unscrew the plastic cover and re-install it in a new can. [You can sign the old can with a permanent marker to detect unauthorized substitutions.]
These are special for a number of reasons:
We don't manufacture these yet, but you can make a generic one by using the slider against the upper ledge of the sleeve to put a slot into the side of your can like this:
You can use rivets to lock-in the slot cover.
This Youtube video shows how a $0.03 rivet is installed, using a $15 rivet gun.
If you haven't made a can lid that's unopened, then you can get by with just riveting on a used can lid, after removing the lid, like this.
The blue lid version is made by opening the top using a can opener, procuring a plastic lid, and cutting a slot in the top.
When making the side-slot for the long coinbank, be sure to make the slot a few millimeters below the upper rim of the inner can. If not, there will be insufficient internal bracing, and you'll bend the can walls.
This also makes a handy swear jar.