The ten's digit automatically rolls over.

The original purpose of this was as a life counter for Magic: the Gathering. It's scaled in just the right way that it would fit into the lower half of an MtG card.

Depending on the tolerances you get out of your printer, you may want to scale it up. 

If your printer is well-calibrated, you should be able to get it assembled with minimal sanding even at a 80% scale.

You'll need some superglue to glue the ten's digit plate to its base. It's designed with a very loose fit, to allow gluing it in just the right orientation.

Great to count life points, victory points, wound damage…